If we are discussing the levels in sa1 and 2, I think sa2 is superior
If I may, I decided to replay both of these games, the game cube versions.
Here is my assessment.
Ahem..
Why did everyone magically forget that Amy's gamma's and big's stages were kinda bad. Really bad, to be quite honest, the egg man stages in sa2 were better than gama's especially the last ones. Sonic stages in Sa1 along with another problem I will mention later , were weird. In sonic adventure 2 with sonic and shadow the stages aside from that weird sonic stage with the weird puzzle at the end( you know what I am talking about) and the pyramid stages most of the stages, let you feel... well like you were rolling around at the speed of sound. Too many of the stages in sa1 made you just stop, it was jarring. I don't particularly mind changes in gameplay, for many games they are a good change of pace., but these abrupt stops were quite jarring.
Next the issue I kind of addressed earlier, the reason I liked sonic adventure two stages more than one is because they were , for the most part different. Sonic in SA1 essentially ran though everyone's stages. And had unique stages all to his own, in Sa2 while there are some stages that share themes, the set up is completely different.I feel like the characters are contributing to something rather than just tacked on.
Next, Tails should not have been playable in sonic adventure 1 or sonic adventure 2. Tails entire campaign in sonic adventure one was basically following sonic around, and you get to fly a plane once. In sonic adventure two where they could have let him run around and have unique stages, they decided to exclude him, when fans roared and they decided to include him they gave him a walker ship thingy like eggman and decided to have him do missions like that. That ship thing would have been alright for 1 many 2 missions( the space ones) but why is he in that thing the entire campaign. Here is my thing, if Sega makes a new sonic game, and say they let other characters like shadow be playable, if they don't have sepreate stages don't event put them in the game.
Back in the 2d days different characters had different things they could do , which would allow them to explore stages differently. But now a days characters are WAY faster than others, and stages are a bit more linear. If they give tails or shadow different stages, that they could solve their own way, that would be fine but if its just sonic's stages over again running through as a different character. What is the point? Offer me new gameplay experiences,use the character potential for different gameplay mechanics to your advantage, i just don't wanna run through sonic's campaign as a new guy.
Also on the treasure hunting stages are way better than people give them credit for, in both games, They need to be fleshed out a bit more though.
While I am ripping on the adventures, Let me rip on some other sonic games.
Sonic heroes, is the worst parts on sonic 06 to me. Just forcing two other characters you don't even want to be involved with slowing down game play.
Shadow was terrible, and not for just being bad, It was terrible because it was a good Idea squandered, that could have been "easily" executed, and almost everyone saw it. A shadow game more focused around combat than running , that sounds very interesting, too bad they jammed running in there. If they attempt that again , I hope they go a more DMC route and just stick to mostly combat and have the running parts just be a way to get from area to area.
Speaking of shadow the hedgehog
Why can tails have a plane with guns and missiles, and eggman have a war ship and a death star. But shadow picks up a gun , the least threatening out of the things I just named and all of a sudden its taboo. And sonic can snow board and tails can fly a plane, but shadow decides he is into motorcycles its wrong for some reason? And yes I know shadow is still super popular , but still it annoys me when people make bullshit excuses for " i like these characters better"
Sonic 06.... its bad and it had some good ideas. And it was rushed, we know the deal.
Unleashed, should have kept it as the world adventure thing.
Generations. Despite all I just said, this game would be the only game it would be acceptable in the new age of sonic to have another character play over sonic's stages, and you could sell as DLC and no one would care. I have played a shadow the hedgehog mod for generations pc that lets you ride shadow's motorcycle on the snowboard parts, and do tricks on it. YOU COULD SELL DLC AS SO MANY EFFING CHARACTERS AND NOW ONE WOULD BE ABLE TO ARGUE AGAINST YOU. SEGA MARKET YO SHIT.
Sorry this tangent went longer than expected.