I only really enjoyed Sonic's and Shadow's stages. Eggman's stages were okay...Tails' were really boring. And don't get me started on the emerald hunting stages.
Overall, SA2B is a fun game but I don't considering it one of the best Sonic games.
The Chao Garden is a really nice addition to the game. A lot of replay value :>
Also, classic Sonic is boring?! What?! Oh well, it's your opinion. (As long as you don't claim Sonic 06 being a good game, I won't hurt you. :P)