I person think that on old skool consoles, the music was amazing, even if it did'nt sound realistic so please put disccuss!
Personally, my favorites are:
Vampire Killer - Castlevania (series)
Jungle (Level 1) - Contra
Super Mario World Theme - Super Mario Theme
SMB2 Overground Theme - SMB2
Moon - Duke Tales
Song of Storms - Legend of Zelda: Ocarina of Time
Pollyanna - Mother (series)
Grabbag - Duke Nukem 3D
Underground - Super Mario Bros. (series)
Birobuto - Super Mario Land
Megaman 2 Theme - Megaman
Megaman 3 Theme - Megaman
Not in any paticular order.