I'd be surprised and disappointed if all his songs were from the 3-D Games, considering that his 2-D games had some of the best game music soundtracks...
While it's unlikely, Songs from Sonic CD would be great, have you ever heard the theme for Metallic Madness (Past)?
If not, here:
http://www.youtube.com/watch?v=0S5xzSGhFng
Green Hill Zone, even though I'll hate that song for all time, will probably be chosen for his stage, so that song can't be overlooked.
Then there's the great songs from Sonic 2: Emerald Hill, Mystic Cave, Hilltop Zone, to name a few...
Sonic 3 and Sonic & Knuckles: Mushroom Hill, Flying Battery, Angel Island, Hydrocity, etc...
The list is almost endless...