There's a high barrier of entry for modding a closed source game written in assembly for specific hardware. Once you're mucking around in assembly you might as well go all the way and change more than just layouts. I think its been said before but I'd expect far more single level mods for mania engine as it was clearly designed with customilability and portability in mind.
Adding to this, hacks like 16-Day Challenge and Sonic Boom deserve more love too (not sure if the latter was intended to be one zone, but it feels like a standalone package). There are examples out there that aren't just "incomplete" TC hacks, and they should be more frequently recognized as complete products that actually finished what they set out to do, by design.
I'll play Boom or Next Level till the cows come home but they do always leave me hungry for more. So I always hope people feel bold enough to go for the full package, but definitely appreciate one super polished level that does what it sets out to do over yet more GHZ flavoured what-could-have-beens. I think Boom was supposed to be a full game but could be wrong, it's been ages. MarkeyJester's done enough one-shots that I always kinda wished he'd try and wrassle them into one cohesive experience somehow, but as they are they're still some of the first mini-games I'd reach for under the gun of "oh shit i only have ten minutes to have a satisfying game experience".
I think Clownacy nailed it on the first page. Really it's a matter of Sonic's level chunks not being very easily module. As a kid who only knew how to get Esrael Sonic Editor II working with his non-disassembly setup of Sonic 1, it was really difficult making anything that felt like it had a decent 'flow' to it. Not to say it was impossible (and I was a dumb kid), but a lot of that was built with very specific purposes that was difficult to re-contextualize. You kinda need to modify the level chunks to make something that has more of a flow to it and I think that's where a lot of the lack of 'little' ROM hacks stem from. Something I've also noticed in the Sonic hacking scene as a whole has had a lot of 'gimmick' hacks where the player plays through what is relatively the same game again (or the same Zone), but there's a gimmick attached that approaches how you interact with everything in the level. Like Red Rings that bounce up and down and suck the life out of a Hedgehog, or playing through the game again as a chattermouth Gecko. It's really interesting to me because these sort of 'gimmick' hacks aren't something I typically see in other ROM hacking communities unless you count bugfix/improvement patches. Mario World doesn't really have any hacks where you say play as Wario with his moveset from Wario Land 1 or anything. Sonic is kinda unique in that regard. (Not that any of this is bad or I want to shun creators for choosing to make such hacks! It's just an observation I made.) I think some of that plays into the complications mentioned earlier in here.
There's also Sonic the Hedgehog: Extended Edition, which adds stuff like world maps, a save system, NegaRings, and such, but it hasn't really got any releases beyond the very first one. I wonder if the hack's still being worked on.
there are thousands, and thousands of Super Mario Bros hacks like the ones above. Character replacement hacks were like the very first hacks to come out in the late 90's. You can find all sorts of stuff like Link in SMB, Carnage in SMB, Contra in SMB, *SONIC* in SMB, and so forth. SMB character replacement hacks were the single most common hacks period in all of rom hacking for many, many years. Nesticle made making such hacks pathetically easy.
My apologies for my earlier message! I realize I wrote a lot of that really vaguely and wasn't terribly specific as to what community I was looking at in my example, so the whole thing I wrote comes across as ignorant. You are indeed correct in that Mario Bros. 1 sprite hacks are dime a dozen, but I had not initially thought of it while I was writing that message. Instead, I was actually looking at Super Mario World specifically. Mainly because it has the most 'active' hacking community I can think of out of all the traditional 2D Mario platformers (at SMWCentral) and both are around the same age (comparing that game's original release date to Sonic 1). I guess what I was trying to get at in my original message is that I've noticed there are quite a few gimmick hacks for Sonic 1 (and Sonic 2 to an extent as well) where the player plays through relatively untouched level designs, but something is added that completely changes how the player is intended to interact with these levels. I already mentioned Red Rings, but then you also have stuff such as Omochao Edition which intentionally punishes the player with obnoxiously long pauses for minor actions (so the goal then is either a sanity test or to get through the level while avoiding as many actions as possible). There are also a couple of others I can think of like Lose Tails or Else, Sonic 1 Bouncy Edition, Sonic 1 Genesis (Genesis), Sonic 1 Return to the Origin, or Sonic 2 XL. These are all hacks off of the top of my head I'm vaguely familiar with where outside of the physic changes/the new challenge, you're still playing (something close to) the same level designs you're already familiar with. A lot of modern Sonic 1/2 hacks that add new playable characters also give them entirely new movesets/abilities that you simply didn't have access to in the original. I guess Bouncy Edition might technically fall under this category, but stuff like Sonic 2 Pink Edition gives Amy a whole new moveset based on how she played in Sonic Advance 1. Most Bros. 1 hacks I'm familiar with don't really alter Mario's moveset in the way of giving him entirely new abilities. Most stuff I'm familiar with when it comes to Bros. 1 are small physic changes (like porting SMB2J Luigi). This isn't to say they simply don't exist (there's a rather attractive looking Celeste-styled hack I completely forgot about until going back through RHDN and a Sonic in SMB1 hack), but there's a lot less of them. Some of it is due to the age of the Nesticle-assisted hacks you mentioned where hacking tools were super limited, and some of it is probably due to there being less interest. Mario World does have individual patches that let you play as other characters on SMWCentral, but there isn't any sort of hack I'm aware of where you can play through the entirety of Mario World again but as Sonic with a moveset similar to his moveset from the Genesis trilogy. I'm also not really familiar with any sort of hacks of Mario World where you play the same game again but Mario say won't stop repeatedly jumping or a single coin immediately kills him regardless of state. They don't really seem to exist. Some of that might be due to hack submission guidelines there, but even looking elsewhere I seem to have trouble finding something like that. (None of that is meant to be a dig at anyone over there! I understand having more strict guidelines in cases like this.) Of course, I realize it is ignorant to just look at one particular ROM hacking community when making such extreme comparisons. I guess I mostly just did it because Mario World and the Sonic trilogy are the ones I keep a close eye on.
I didn't meant to imply that SMB hacks were changing gameplay like in the Sonic hacks, merely to say that there indeed were partial conversion hacks for Mario games. If anything, this kind of gets to the entire heart of the conversation -- the easier the tools, the more hacks are created, but the limitations of the tools also dictates what kinds of hacks or TCs are created. Nesticle offered no real way to edit levels or mechanics or anything, only art and palettes, so that's the kind of hacks that existed. DOOM's WAD format and tools led itself to more easily distributing single level or megawad packs. The nature of Sonic hacking and the tools available makes people swing for the fences if they're gonna try this stuff. Another good series to look at is the NES Zelda. Those games actually did have a ton of megawad style rom hacks, because editing dungeon layouts is actually pretty easy in the Zelda rom.
