I've played all the main ones (and some spin offs) except Color and CD, but haven't finished all of them. However for the topic I will say this:
Sonic 2 is my favorite. No, this isn't nostalgia speaking, since I first played it on the DS. I played Sonic 1 and 3 as well, but they just never captured me like 2 did. Whenever I play them, I just keep coming back to 2. I don't know, always preferred the music and level design of 2.
Sonic Generations is close to it though, because both 2D Sonic and 3D Sonic (holy ****!) were great and fun to use, with some excellent level design and no annoying friends to play as. The game was just full on fanservice, and not the ****** kind we've been seeing for the past either. Loved this game, only bad part was the final boss and the short length. (And 2D planet wisp! ugh)
Everything else I hated though. Adventure, Adventure 2, Unleashed, Heroes, Shadow and especially 2006 just made me pull my hair off. Awful controls, awful level design (Adventure 2 actually nailed this though, if memory serves right. everything else no, aside from having Eggman as playable) and they all lack polish. 2006 is easily the worst game I have ever played, bar none.
I also liked Rush and Rush Adventure a lot, but can't say the same for Sonic Generations 3DS. I gotta give both Sonic Colors games a try some day.
This message has been deleted by
Elendil. Reason:
Not wasting 1000th post on Sonic.
haha
EDIT: I also feel the need to say that Sonic and All Stars Racing Transformed is really REALLY good. Though more of a SEGA game generally than an actual Sonic one, it deserves a mention. Up there with Mario Kart DS/7 and Crash Team Racing as my favorite kart racer of all time.