Oh to the heck with it, the classical Sonic music is also amazing. Starlight Zone from Sonic 1, Chemical Plant from Sonic 2, Launch Base Zone from Sonic 3, and Flying Battery Zone from Sonic & Knuckles are some of my favorite tracks.
Too many to list for 3; I only really know Emerald Hill, Casino Night and Chemical Plant from 2, though; haven't really listened to a ton of the songs from 2 yet. =P