Funnily enough, Sonic Adventure 2 doesn't list Sonic 3D (or Sonic CD) as part of the main series. =P ...And yet it lists Sonic Jam, of all things.
Possibly because it had Sonic World, which was a proto-Sonic Adventure. Yet more evidence that 3D Blast wasn't part of Sonic's evolution from classic to Adventure.
Didn't SEGA treat 3D as being mainline back in 1996? I mean, that was the big holiday release for Sonic. It was THE Sonic game for the Saturn. It wasn't the one that was supposed to come out, obviously, but it's the one that Sega ended up promoting as the next big thing.
What Sega of America’s marketing team says and what the developers think of a product is very different. That list from SA2 pretty clearly shows what Sonic Team considered to be the “core” titles in the series.
Maybe, but 3D had big Sonic Team members working on the game design. Iizuka worked on the general concept, Yasuhara worked on the level design, and Senoue did the soundtrack. And it is a Sonic platformer for home consoles. I think the developers, in this case, would've considered it a core entry back then. It could be left off the SA2 list for any number of reasons, like how the Genesis version wasn't released in Japan and the Saturn version only got a limited aftermarket release with no fanfare. Consider that Super Mario USA (our Mario 2) was not considered a "core Super Mario game" in Japan for a long time after its release either. And I think it's pretty silly to think CD isn't a core entry based on that list, since Sonic Adventure certainly treats it as being one and it had a whole damn OVA based on it. In fact, SA2's list reminds me of that one cutscene in Super Mario Sunshine where F.L.U.D.D. gives a list of Mario games which all seem like "core" entries, except neither Mario Land nor Yoshi's Island are on there, and instead we have...the Mario Kart games. If you go on Nintendo's website, for both America and Japan, it has a list of "mainline" Mario games, however Sonic has no such thing. Sonic Channel lists basically every Sonic game ever made and makes no distinction on which ones are "core" or not. Even the Encyclo-speed-ia lists them all under the same banner. I'm not even sure if SEGA has an internal document listing "core" entries or not. Who cares? It's all product! Buy buy buy!
I dunno. Would the Japan-based Sonic Team have considered a game created exclusively for the western market mainline? I'd think something as important as a core game would have been given a global release (even if not simultaneous). And it wasn't just a case of "the MD was unpopular in Japan so the game was skipped there", as the Saturn port was similarly skipped at first despite the Saturn selling the best there. It was only released years later on the very same day as Sonic Adventure International, effectively treating it as a side game to accompany the main installment. You know, like the MD version was intended to be to X-treme.
My question is, at the end of the day: Who fucking cares? It's a Sonic game, ultimately. The "mainline" vs. "spin-off" distinction is pretty irrelevant in the grand scheme of things.
It should matter, but it's been proven several times in several fields of knowledge that accuracy isn't the key goal of Wikipedia, at least not anymore.
Unless it is explicitly stated, one can’t take as gospel what is written as an indication that the game is or isn’t considered a mainline title by SEGA. Sonic CD isn’t always listed, yet it is quite clearly a core Sonic title based on its influence on later titles, such as Sonic Adventure, Sonic Heroes, Sonic 4, Sonic Generations, Sonic Mania, as well as the latest compilations. Sonic 3D fits quite distinctly between 3&K and Sonic Adventure, and has a soundtrack that heavily influences later games. It, however, depicts events that are generally unimportant to the progression of the series as a whole. It is likely that this is the reason that it is often overlooked in the grand scheme of things, coupled with it not being a Sonic Team game.
I feel like using Generations as a baseline is the closest we'll ever get to the definitive answer to this question. Going by that game, the mainline titles are as follows: Sonic 1, Sonic 2, Sonic 3&K, SA1, SA2, Heroes, 06, Unleashed, and Colors. CD also gets an honorable mention of sorts in the game via the Metal Sonic boss fight due to it's influence to the series, but it's still not technically mainline due to not having it's own stage. 3D Blast only has a singular unlockable music track, but so do undebatable spinoff games like Riders so you can't say that means it's mainline. After Generations though, the question of what's mainline gets significantly less muddy of course as it's pretty obvious to anyone that the mainline titles after it are Lost World, Forces, and Frontiers, no debate about it.
This gif literally comes from a game (well, its trailer) that has Sonic CD levels, lol. Feel like this came up before, but yeah, I have no beef with 3D Blast being considered mainline. Sonic Team was more involved with it than something like say, Spinball, it was a flagship title at the time of its release, etc. Is it an easy candidate to exclude if we're trying to narrow it down to the "important" ones? Sure, but ultimately I'm not terribly concerned with its status either way. Helps that I'm also more partial to the game than most of the Sonic fandom seems to be, so there's that.
The line between mainline and spin-off is so blurry that there really is no definitive answer. Is Sonic the Hedgehog 4 a mainline game or a spin-off? I guess it's mainline because it's called Sonic the Hedgehog 4. But it also didn't get a physical release like the other mainline games at the time like Sonic Colors and Generations. Is Shadow the Hedgehog a spin-off? It doesn't have Sonic's name in the title so maybe? And how about Secret Rings and Black Knight? Or the handhelds like Sonic Advanced and Sonic Rush?
So yes, last year there was a topic about this question in a more broad sense. I'm not sure how much different this topic will be from that one if we continue on, but I won't be locking it just yet, I guess. What is "mainline" isn't a question about canon. Canon is a completely different question. Spin-offs can be canon. Comic books can be canon. Mainline games are mainline. Whatever that really means. Right, because Sega would want to push the Sega Saturn at a trade show, while 3D Blast is just something to keep the older hardware somewhat relevant. And yet 3D Blast is a game that was conceived and designed by members of Sega of Japan and Sonic Team. So what is the line where a game is a "Sonic Team" game and not? The programming? The sprite work? Even if 3D Blast really was just meant to play second fiddle to X-treme, it was thrust into the spotlight when the latter game was cancelled. "Blue is Back," the 5th anniversary push, focused on 3D Blast, making it sound like the next mainline title. Again, whatever that means. A lot of it is arbitrary, in an attempt to classify things. Because if there's one thing people love to do, it's sort and classify things. I mean, just look at the wiki. We love to do it, too.
I believe the "Blue is Back" thing was used around that time for a number of games that came out then, not just 3D Blast. From that very link: We're not going to start debating whether or not the GG and Pico games are mainline now are we? Anyway, I think a key point about the discussion is that 3D Blast isn't treated as mainline by the current Sega, nor was ever treated as such by Sonic Team or SOJ. Note how it never gets any mentions or references, unlike the mainline games. SOA advertised it as the biggest Sonic game of the year back then, but then again they did the same for Spinball when it came out as stated in this thread, so that doesn't mean a lot.
I think we need to establish what ‘mainline’, means, versus ‘sideline’. For clarity, I presume most, if not all of us, mean for ‘sideline’; a game that is canon, fits within the timeline and narrative of the story, but not created by the core team and not essential to forward the plot of the games?
If the question is if 3D Blast is canon or not then the answer is yes it is. We just went back to Flickies' Island a few weeks ago in the IDW comics.