Favorite Sonic games are 2, S3&K, SA2, and Generations.
Favorite soundtrack for a Sonic game would have to be Sonic 3 & Knuckles if only for the Michael Jackson rumor.
Best level music in a Sonic game would be Mystic Cave Zone from Sonic 2.
Then again, my brother has ALWAYS been a bigger Sonic fan than I am. Sonic Adventure 2 is his all-time favorite video game.