[BlackHole]

Welp, here's a thread for those of us interested in sharing theories and headcanons. Please don't get into arguments, debates, sure, but don't be jerks during one.

Because I'm in a bit of a rush, I'll post my up-to-date Sonic Timeline theory:

BlackHole, on 30 November 2014 - 09:31 PM, said:

Spoiler

]Tails' Adventures

Spoiler

Outright said to be before Sonic and Tails met, I believe this takes place contemporarily with...

Sonic the Hedgehog (both)

Spoiler

The levels weave in and out of one another: 8-bit Green Hill goes to 16-bit Green Hill, then Sonic crosses Bridge Zone to get to Marble Zone, which sits outside Jungle Zone, which Sonic goes through to get into the newly fortified former residential Spring Yard Zone, which has an entrance into the Labyrinth Zone, etcetc.

Sonic the Hedgehog 2 (8-bit)

Spoiler

Tails jumps across to South Island in order to catch a ride to go see the Little Planet.He never really sees Green Hill Zone, instead hanging around the Marble Zone because the ruins interest him and he's fearful of people due to his treatment from them prior, but one day a blue blur passes while he's wandering the Jungle Zone, a la a cutscene from Sonic Adventure. He follows, they become friendly and one day Robotnik picks him up during a raid, leading to the game...

Sonic Chaos

Spoiler

Between Sonic 2 8-bit and this game, Sonic manages to master the Spin Dash and Tails mimics him, prompting the Hedgehog to consider him a little brother outright instead of just a friend. Tails, happy by this acceptance, shows off various gizmos to Sonic, such as the Rocket Boots. Then Robotnik manages to snag the Red Chaos Emerald, cue the game.

Sonic Generations (Classic Sonic)

Spoiler

During a run through Green Hill, Sonic notices some Badniks and deals with them promptly. The Badniks were bait, however, and Sonic is drawn into the plot...

Sonic Schoolhouse

Spoiler

The people of South Island, thankful for Sonic's assistance, construct a schoolhouse in his honour, with a holographic interface of him to teach the children, though they note there's quite a few bugs in the software at the moment...

Sonic CD

Spoiler

South Island comes into view of Westside Island, allowing Sonic and Tails the opportunity to go see the Little Planet, as per Sonic 4. The games events go on, but while on the Little Planet, Sonic can't quite get used to the different gravity in order to execute a proper spindash. Tails, meanwhile, goes on his lonesome to explore the planet.

Sonic the Hedgehog 2 (16-bit)

Spoiler

G.U.N. locate the Death Egg under construction, forcing an early launch when they attempt an assault. Robotnik proceeds to assault Westside Island to capture more labour to finish construction quickly while in orbit, but being the egomaniac he is gloats to Sonic about it, prompting the events of the game...

Sonic Drift and assorted spinoffs (aka those not listed on here)

Spoiler

With Sonic's heroism coming to light, many productions in his image are made on the recovering Westside Island, including cartoons and games.

Sonic Spinball

Spoiler

With the Death Egg down, Robotnik retreats to Mt. Mobius to use the resources to rebuild the Death Egg in Angel Island. Sonic and Tails hear word of Robotnik's mass Badnik production and decide to strike first, leading to the events of the game.

Sonic the Hedgehog 3

Spoiler

As said in the Japanese manual, Sonic and Tails find a relic on Westside Island's beach and learn of the Death Egg's survival and Angel Island, prompting them to immediately fly on over.

Sonic Triple Trouble

Spoiler

With the Death Egg downed again, Robotnik 'accidentally' launches the Chaos Emeralds Knuckles gave him after nicking them from Sonic in Sonic 3 to the four corners of the world with a 'misfire' of the Death Eggs weapons, prompting Sonic to go after them instead to keep them safe. This gives him time to properly rebuild the Death Egg, much quicker as well since Knuckles is also off the island. Robotnik goes after them as well, even sending a second Metal Sonic after them, if only to keep up appearances as he's discovered a much larger energy source on Angel Island...

Sonic and Knuckles

Spoiler

With the Chaos Emeralds safe, Sonic immediately returns to Angel Island. After Tails drops Sonic off in Mushroom Hill, since the Tornado can't get in close because of strange weather patterns causing turbulence, Sonic goes it alone while Tails stays with the Tornado incase the Death Egg manages a take off again as it did in Sonic 3. Cue Sonic and Knuckles (Sonic section)...

Sonic 3 and Knuckles (Knuckles Story)

Spoiler

Knuckles, angered with Robotnik's betrayal, proceeds to destroy all the obvious bases on Angel Island (the Sonic 3 portion), before deciding to relax in Mushroom Hill. However, he's attacked by a certain Badnik, kicking off the Sonic and Knuckles section.

Sonic the Hedgehog 4 Episode 1

Spoiler

Upon Westside Island, Robotnik attacks in a show of force from an E.G.G. Station in orbit. This is to distract Sonic from what remains of the Death Egg being salvaged in preparation of the Little Planet. Upon destroying the E.G.G. Station, Sonic uses the rocket to return and the Tornado, placed where Sonic would land via Tails calculations, to return to Westside Island. As Sonic does so, he notices a commotion on the Sky Sanctuary and circles until he can assist...

Knuckles in Sonic the Hedgehog 2

Spoiler

As Knuckles now owes Sonic his life twice over, he agrees to help Sonic deal with the remnants of Robotniks' remaining forces on Westside Island in the same way he dealt with them on Angel Island before Tails takes him back. As Sonic deals with the E.G.G. Station, Knuckles deals with the Badniks alongside Tails, since Knuckles isn't familiar with the land. Knuckles even proceeds to take out a chunk of the Death Egg that has managed to remain active. However, they all fail to notice the robot leaving the Mad Gear section of Metropolis and making a beeline for the Lost Labyrinth...

Sonic the Hedgehog 4: Episode Metal

Spoiler

As the Little Planet approaches, Robotnik contacts the Stardust Speedway facility and uses what power it has to get the original Metal Sonic back home and powered up, as in the game.

Sonic the Hedgehog 4: Episode 2

Spoiler

As the Little Planet approaches, everyone is horrified by the appearance of a familiar metal skeleton around it as the salvaged Death Egg is constructed around it. Sonic and Tails immediately hop into action, Knuckles home on Angel Island, but both are followed by a familiar robot...

Sonic Labyrinth

Spoiler

Robotnik, irate and thoroughly angered by his constant failures through Sonic, decides to enact revenge. Using a robot to sneak into Sonic's resting place, he decides that death is too easy as option and instead decides to humiliate the hedgehog in the same way Sonic has humiliated him countless times: swapping out the shoes for ones that hold his feet down, he taunts Sonic and captures him as in the scene from SEGASonic the Hedgehog, taking him to one of his many island fortresses, this one known as Carnival Island that is being used as a base while Robotnik attempts to locate the Chaos Rings, before making him navigate the maze in a twisted game. When Sonic completes the mazes, however... he is immediately dumped back into a cage for Robotnik's leisure, where he meets a young squirrel named Ray.

Tails Skypatrol

Spoiler

With Sonic currently missing in action, Tails steps up to protect the island from several new bad guys whom claim Westside Island for their own.

Knuckles Chaotix

Spoiler

Knuckles, spotting Carnival Island from Angel Island, feels a familiar energy. He goes to investigate, being drawn by the Chaos Rings, before interrupting Robotnik as he tends to Espio the Chameleon. The events of the game pan out...

SEGASonic the Hedgehog

Spoiler

After Knuckles Chaotix, Mighty immediately returns to Carnival Island to locate an old friend, Ray, as he was why Mighty was there in the first place. Being captured and thrown into the same cage as the other two, the other facilities to damaged by the Chaotix to hold them, they all manage a breakout and proceed to finish off the Carnival Island base, though with the Chaos Rings gone Robotnik feels there was no more point to the base anyway.

Sonic Blast

Spoiler

Robotnik decides to shove caution to the wind and just shoot Sonic, but instead accidentally hits the Chaos Emeralds and scatters them again. Knuckles, looking for Tails to catcha ride back to Angel Island, agrees to help Sonic fight Robotnik once more.

Sonic 3D: Flickies Island

Spoiler

Calming the hell down after his revenge plot, Robotnik decides to start from scratch on Flickies Island and immediately begins constructing an army as he did on South Island. Sonic, Tails and Knuckles all head for the island to stop Robotnik, Knuckles tagging along as he still feels he owes Sonic his life.

Sonic R

Spoiler

Seemingly losing his mind again, Robotnik organizes a race with Sonic and co, but his planned courses have Sonic worried as they all seem curiously close to where he has hidden the Chaos Emeralds...

Sonic the Fighters

Spoiler

The Little Planet comes around once more, still held by the Death Egg (since Sonic 4 seems to have been abandoned). Robotnik immediately pounces and uses it to construct an army, adding more modules to increase production. As the world fends off the invasion, a minor fight breaks out over the Chaos Emeralds and whom gets to deal with Robotnik...

Sonic Mania (Plus)

Spoiler

Sonic and Tails travel to Angel Island at Knuckles' request, as Angel Island has mysteriously crashed into the water once more. Upon their arrival, however, they encounter EggRobos, lead by the EggRobo of Sonic R, digging up an odd jewel that proceeds to interfere with the world around it.

Sonic Forces (Classic Sonic)

Spoiler

Due to the influence of the Time Stones ambient energy on Little Planet, similar to how it absorbed the energy of the Master Emerald and caused Angel Island to crash, the Phantom Ruby displays the point in the future when it becomes active again as an illusion for Sonic to interact with. Tails and Robotnik, as a result, mistake Sonic as being from another dimension, as they have no recollection of Sonic's absence in the past, disappearing for after adventures just being par for the course with him. The Phantom Ruby 'remembers' this and enacts it as an illusion once the correct time comes, unable to stop itself as it wasn't meant for the power of the Time Stones and thus cannot control it.

Sonic Mania Adventures

Spoiler

With the Phantom Ruby inactive until the future, Sonic reappears to the world on Angel Island, another effect of the Time Stone-empowered Phantom Ruby. Upon seeing Robotnik continuing his usual ways, Sonic springs into action.

Sonic Pocket Adventure

Spoiler

After so many defeats, Robotnik hits a slump and finds himself unable to develop new Badniks. Instead, he employs some old excess badniks in an attempt at grabbing the Chaos Emeralds. After his defeat, Robotnik decides to take a year off to try and reinvigorate himself.

Sonic Jam

Spoiler

Sonic, now a worldwide hero, receives a museum dedicated to his actions: the Sonic Journey Accumulation Museum. A recap on his journey up until now, he decides to have a proper holiday while Robotnik is being quiet, taking about a year off until he eventually turns up in a place called Station Square...

And the timeline mentions a second Metal Sonic during Triple Trouble. That isn't a random addition, that Metal Sonic is damaged and refurbished by Robotnik with knowledge garnered during Generations, building the Metal Sonic seen in Sonic 3 and Knuckles from TT Metal Sonic's remains.

Please, share your theories, I'd be interested to hear them all.

This post has been edited by BlackHole: 09 April 2018 - 12:04 PM

[Laughingcow]

It's worth pointing out that Metal Sonic didn't become an actual character until it was established in Sonic Heroes (which borrows from the Sonic OVA). Before that, he was just one of Robotnik's robots along with Mecha Sonic.

We need to keep in mind that until Sonic Adventure, there wasn't much of a need to establish a consistent series of events. The games in the classic era could be considered like episodes in a cartoon where everything happens but doesn't necessarily need to happen in order. As I said in the previous thread, the attempt at telling an RPG styled grandiose story is where things breakdown. In trying to tell a bigger story they only create more problems for the later games to come which lead to retcons and plot holes.

In addition, Sonic Adventure wasn't the only soft reboot. Sonic Generations (thanks to its time fuckery) was a new baseline, a "get out of continuity free" card if you will. History was literally rewritten so any inconsistency can be hand waived away as no longer mattering. I don't think Sonic Team intended this but it is convenient.

Lastly, I'm gonna repost what I posted in the other thread about the Mario timeline.

Actually Shigeru Miyamoto has said many times that mario games are "timeless" and don't have a real canon to them. This becomes apparent when you realize that the Super Mario Bros. movie is actually holds some weight as this quote shows:

“This is an old story, but Hollywood did a film version of the Mario Bros. many years back. There was a scene in the script where they needed a last name for the characters. Somebody suggested that, because they were the Mario Bros., their last name should be Mario. So, they made him “Mario Mario.” I heard this and laughed rather loudly. Of course, this was ultimately included in the film. Based on the film, that's [how] their names ended up. But, just like Mickey Mouse doesn't really have a last name, Mario is really just Mario and Luigi is really just Luigi.”

https://nintendoever...is-mario-mario/

So, Miyamoto dicking around seems to make a better continuity then actively trying. Of course. Maybe if we got Yuji Naka, Takashi Iizuka, and Yu Suzuki drunk in the same room they'd give us the timeline we've been lookin for.

This post has been edited by Laughingcow: 08 April 2018 - 05:35 PM

[Overlord]

We uh

Kinda don't do this sort of thread on Retro, really. It's in the ruleset and everything.

http://forums.sonicr...showtopic=11220

Quote

12. No half-assed "theories."

Since the earliest stages of the Sonic community's inception, there has been speculation regarding certain aspects of Sonic game development. As a result, many members would make "theories" to try and explain what could not be backed up by any sort of concrete evidence. The problem with this, however, is that about 99% of "theories" were total crap and did not make any sense whatsoever.

If you wish to post any speculation on the board, then realize that it is up to you to back up your speculation with concrete evidence. All theories and ideas must be supported by facts and elaborated with reasons. The burden of proof is on YOUR side to support the theory, not on ours to debunk it. Generally, opinionated theories are obsolete as they've been replaced by fact-oriented research. DO NOT start any theory unless you know what you're talking about.

Headcanon kinda falls under this.

[Sparks]

Is that for game development specifically or just theories about the games lore overall?

I think it's at least worth experimenting this kind of thread as a stand-alone concentrated "filter" thread, as judging from the Mania thread, it does seem to be a hot topic a lot of people want to discuss.

[Vangar]

I was sure that rule was added when we got sick of people making up theories and trying to push them as real about tails owning the master emerald in Hidden Palace, stuff like that.

I have a head cannon that nothing past Sonic 3 & Knuckles ever happened (And Mania)

[Hitlersaurus Christ]

My theory is that Sonic is actually a real hedgehog that came across and ingested a large quantity of LSD and the entire franchise is just what he's seeing.

[doc eggfan]

I don't think everything needs to be in one continuous timeline

Epoch 1
More traditional platforming, no spin dash

• Sonic 1 (16-bit)
  
• Sonic 1 (8-bit)
  
• Sonic 2 (8-bit) {bridging epoch 1.5}

**Timeline splits in two**

Epoch 2
Levels with more horizontality, plus spin dash. Death Egg arc, part 1.

• Sonic 2 (16-bit)
  
• Sonic Pocket Adventure

Epoch 2'
Levels with more verticality, plus super peel out. Metal Sonic arc.

• Sonic Chaos {bridging epoch 1.5'}
  
• Sonic CD
  
• Sonic Triple Trouble
  
• Knuckles Chaotix (epoch 3' maybe?)

**Epoch 2' terminates, Epoch 3, follows Epoch 2**

Epoch 3
Level design good balance of horizontal and vertical, plus elemental shields. Death Egg arc, part 2.

• Sonic 3
  
• Sonic & Knuckles

Epoch 4

• Sonic Mania
  

That's about it for the mainline classic 2D series, in my mind. The rest could be dismissed as "non-canon" spin-offs.

This post has been edited by doc eggfan: 09 April 2018 - 08:20 AM

[SoNick]

Overlord, on 08 April 2018 - 05:25 PM, said:

We uh

Kinda don't do this sort of thread on Retro, really. It's in the ruleset and everything.

This is actually what I came into the topic to say as well. This is a research site, not fanfiction.net.

[Hitlersaurus Christ]

My theory is that rings are actually robotnik's poop that he leaves everywhere for Sonic to clean up.

They look that way because he has a rare intestinal condition. He is sick. Sonic is picking on a sick old man. Much like God of War, Sonic is a game where you play as the villain.

This post has been edited by Hitlersaurus Christ: 09 April 2018 - 06:36 AM

[XCubed]

SoNick, on 09 April 2018 - 06:03 AM, said:

Overlord, on 08 April 2018 - 05:25 PM, said:

We uh

Kinda don't do this sort of thread on Retro, really. It's in the ruleset and everything.

This is actually what I came into the topic to say as well. This is a research site, not fanfiction.net.

Exactly. By now I've learned that they do not want a set “timeline” of events. It hinders creativity. The only true conspiracy is Sonic 3's music (which is its own thread) and the Sonic 4 cliffhanger which needs to be concluded with an animation, comic, book, something. But no more therories. If you have one, write a book and share it in the Creative Works forum.

This post has been edited by XCubed: 09 April 2018 - 08:56 AM

[Scarred Sun]

Ugh, headcanon and fanon are... not really our jam here, but I want to see if this goes somewhere. That said, let's set some ground rules:

1. Hello Internet comedians please find another topic to make your jokes. I'm willing to give the benefit of the doubt but if we're just cracking one-liners this topic will have no chance of surviving.

2. If you're going to post any headcanon or fanon theory, you still need demonstrable evidence and a writeup. We're talking corroborating evidence like manual texts, developer interviews, some actual screenshots, promotional content, something. Not two sentences of "I think this."

If it works, it works; if not, this topic will be locked.

[BlackHole]

I've removed the mentions of headcanon and the Robotnik one, make it more inline with the forum's rules. My apologies, I thought I'd shift the discussion from Mania Plus into a thread more suitable towards it, and theories can prove interesting when people are willing to invest time into it. Zelda is rife for it, and some of them are fairly interesting.

Examples of what we could look at are things like the Angel Island pyramids in Sandopolis. Were Echidna are Humans particularly close at some point, since Humans appear in their murals?

[Chainspike]

Correct me if I'm wrong, but I thought the classic games took place on Sonic's world. Humans (except for robotnik) are non-existent in Sonic games up until Sonic Adventure. Except for that carving in Sandopolis Zone act 2 which was likely nothing more than a level artist making the Zone look like an Egyptian Pyramid. They said themselves whilst making Adventure 1, that they wanted Sonic to be in a more realistic world. This was also a main plot point for an entire (non-canon) TV show (Sonic X). Also, it seems like Sonic Forces and Sonic Mania take place in Sonic's world too.


Sonic probably learned the spin dash from this guy: (Image to big)

Spoiler

It actually would unoffically be the first use of the spindash in a Sonic game.

[Hitlersaurus Christ]

Chainspike, on 10 April 2018 - 02:03 AM, said:

Correct me if I'm wrong, but I thought the classic games took place on Sonic's world. Humans (except for robotnik) are non-existent in Sonic games up until Sonic Adventure. Except for that carving in Sandopolis Zone act 2 which was likely nothing more than a level artist making the Zone look like an Egyptian Pyramid. They said themselves whilst making Adventure 1, that they wanted Sonic to be in a more realistic world. This was also a main plot point for an entire (non-canon) TV show (Sonic X). Also, it seems like Sonic Forces and Sonic Mania take place in Sonic's world too.

That's certainly what Sega's going with now, but back when Yuji Naka was with Sega someone asked him why there were humans in Adventure but not the originals and he said it's because the previous games took place on islands where there weren't many humans but the Adventures take place on the mainland.

[DigitalDuck]

Okay, so a fair bit of fanwankery but this is how I see it:

Sonic 1 (8-bit) and Sonic 1 (16-bit) - shared by both Classic and Modern Universes:

Spoiler

Two different tellings of the same adventure. We can even assume the original 16-bit level order (before it was changed for balance reasons) and they still fit together as Green Hill -> Bridge -> Jungle -> Labyrinth -> Marble -> Star Light -> Spring Yard -> Scrap Brain -> Sky Base. They share a lot of locations and is suggested to be Sonic's first meeting with Eggman.

Tails' Skypatrol - shared by both Classic and Modern Universes:

Spoiler

Could take place before, after, or concurrently with Sonic 1 (8-bit)/(16-bit); Tails being Tails before meeting Sonic or Eggman.

Sonic 2 8-bit - shared by both Classic and Modern Universes:

Spoiler

Tails meets Sonic on South Island, Eggman kidnaps him, Sonic saves him. Eggman realises the only thing that would beat Sonic is a robotic version of himself, develops Silver Sonic as a prototype.

Sonic 2 16-bit - shared by both Classic and Modern Universes:

Spoiler

Sonic and Tails chase Eggman to Westside Island, Eggman fixes and improves Silver Sonic, also builds giant Eggman mech. Sonic develops the Spindash.

Sonic 3K - shared by both Classic and Modern Universes:

Spoiler

Eggman hears rumours of powerful Master Emerald on Angel Island, tricks Knuckles into thinking Sonic is the bad guy. Upgrades Silver Sonic to Mecha Sonic, upgrades giant Eggman mech.

Sonic Generations (Classic) - Classic Universe only

Spoiler

Classic Sonic seems to have been pulled right out after S3K - Tails is with him, but Knuckles isn't as he's guarding the Master Emerald and still suspicious of Sonic. Sonic's first encounter with Metal Sonic in the Classic Universe.

Sonic & Tails - shared by both Classic and Modern Universes:

Spoiler

Eggman starts shit again. In the Classic Universe, Sonic tries to develop the air dash after seeing Modern Sonic perform it, but can't quite figure it out. In the Modern Universe, Sonic develops the Peelout.

Sonic 3K (Knuckles) - shared by both Classic and Modern Universes:

Spoiler

Could take place before, after, or concurrently with Sonic & Tails; after Sonic and Eggman have had their little tiff on Angel Island, Knuckles cleans up the place and sorts out that rogue Egg Robo.

Sonic & Tails 2 - shared by both Classic and Modern Universes:

Spoiler

Eggman tricks Knuckles into thinking Sonic is the bad guy again. Fang decides to be an opportunist. Knuckles finally accepts Sonic as the good guy (for a while). Eggman unveils his new, perfect robot Sonic: Metal Sonic... except it's not quite finished yet. Sonic's first encounter with Metal Sonic in the Modern Universe.

Sonic 3D - shared by both Classic and Modern Universes:

Spoiler

Eggman starts shit in Flicky Island, upgrades giant Eggman mech again, continues working on new robot Sonic behind the scenes. Tails and Knuckles help Sonic defeat him. Sonic learns Homing Attack with the gold shield. In the Modern Universe, Sonic practices this until he can do it without the shield. In the Classic Universe, Sonic is too fixated on the air dash to realise the connection between the two.

Sonic CD - shared by both Classic and Modern Universes:

Spoiler

The trio part ways. Sonic saves Amy, spends rest of life trying to run away from her. Eggman starts shit on Little Planet. In the Classic Universe, Sonic uses his previous experience against Metal Sonic and wrecks him. In the Modern Universe, Sonic uses his perfected Peelout to outrun him.

Tails Adventure - shared by both Classic and Modern Universes:

Spoiler

Could take place before, after, or concurrently with Sonic CD; Tails spends more time working on his technological abilities to help Sonic defeat Eggman, finds his own rival instead. While the Japanese manual says this takes place before Sonic and Tails meet, the US/Europe manuals disagree - I think it makes more sense here.

Sonic the Fighters - Classic Universe only:

Spoiler

A very loose adaption of Sonic 4's story in the Classic Universe, Eggman spends a lot of time rebuilding Metal Sonic after Sonic destroyed it. Sonic gathers a ton of friends beat the shit out of Eggman and minions on Death Egg 2. Sonic and Tails go off and do their own thing, Knuckles and Espio go elsewhere...

Sonic 4 - Modern Universe only:

Spoiler

Eggman fucks up Little Planet some more, recovers Metal Sonic and upgrades him, giant Eggman mech, and Death Egg again. Tails returns to Sonic to help defeat him.

Sonic Mania - Classic Universe only:

Spoiler

The Phantom Ruby appears due to anomalies in time, appears "simultaneously" in both the Classic and Modern universes, being much more powerful in the Classic universe as that's where the timeline rewrite is occurring. Classic Sonic's attempts at imitating Modern Sonic's air dash lead to him developing the Drop Dash instead.

Sonic Forces (Classic) - Classic Universe only:

Spoiler

The Chaos Emeralds amplify the power of the Phantom Ruby and allows Classic Sonic to appear, as an illusion, in the Modern Universe.

Chaotix - Classic Universe only:

Spoiler

While Sonic is in another universe, Eggman decides to start shit again, upgrading Metal Sonic some more. Knuckles and co. arrive to save the day instead.

The rest of the games are Modern Universe only and order is effectively game order starting from Sonic Pocket Adventure. I'm not counting most spinoffs in this as they should be considered non-canon.

Classic Universe:
Sonic 1 (8-bit) and Sonic 1 (16-bit)
Tails' Skypatrol
Sonic 2 8-bit
Sonic 2 16-bit
Sonic 3K
Sonic Generations (Classic)
Sonic & Tails
Sonic 3K (Knuckles)
Sonic & Tails 2
Sonic 3D
Sonic CD
Tails Adventure
Sonic the Fighters
Sonic Mania
Sonic Forces (Classic)
Chaotix

Modern Universe:
Sonic 1 (8-bit) and Sonic 1 (16-bit)
Tails' Skypatrol
Sonic 2 8-bit
Sonic 2 16-bit
Sonic 3K
Sonic & Tails
Sonic 3K (Knuckles)
Sonic & Tails 2
Sonic 3D
Sonic CD
Tails Adventure
Sonic 4
Sonic Pocket Adventure
Sonic Adventure etc.

TL;DR: Generations caused Classic Universe Sonic to focus on the air dash, this developed into the Drop Dash; Peelout is a Modern Universe thing, eventually developed into the Boost. Minus Peelout but plus experience, Classic Universe Sonic was more direct in fights against Metal Sonic and caused more damage against him than his Modern Universe counterpart, massively diverging the timelines and creating the Phantom Ruby as a result.

There, you wanted theories.