Sonic games always have great songs on them.
Sonic 1- Green Hill Zone's music is awsome
Sonic 2- Super Sonic music is my favorite here
Sonic 3- the Ice Cap Zone rocks
Sonic CD- the opening theme is the only one I've heard of course that's good as well.
Sonic Adventure 1/DX- "Open Your Heart" is just something else Sonic's theme and the invincibilty themes are good as well.
Sonic Adventure 2- Live and Learn, Sonic theme, City Escape, Aquatic Mines are all great.
Sonic Heros has Team chaotix Team Dark and "What I'm made of" All of those rule.
The cake for soudtracks would have to go to Grand Theft Auto though.
I don't even need to say what rocksabout Vice City's soundtrack.
GTA San Andreas has "Welcome to the Jungle" done by Guns & Roses, "Hellraiser" (spelling?) by Ozzy Osbourne, "Hollywood Swinging" I forget who that's done by though, "Young Turks" by Rod Stewart, "A Horse with no Name", and plenty of other awsome songs.