My rule: One song per game.
Dustforce - 9-Bit Expedition (Note: anything from Dustforce is a fantastic song, this is just my fave of the soundtrack)
Sanctum - The Wanderers
BIT.TRIP RUNNER - Impetus (Kind of, actually a full level because it gives you a good idea of how the gameplay creates the soundtrack to a degree)
DROD - Level 2 (Worked as support for their later games, this was from the original 90s version. Encoded MIDI doesn't do it justice sadly)
Donkey Kong Country 2 - Disco Train (Probably my fave of the three games. 2 had all the best songs though. Remix album was fantastic too)
Super Mario RPG - Slope (Tough call, but one of my faves from the game. Beware the Forest Mushrooms was great too)
Street Fighter II - Guile's Theme (GO HOME AND BE A FAMILY MAN)
Street Fighter IV - Sakura's Theme (Great song for a great character)