You can get loads of midi files here:
Midi Games Music
And I've put a little pack in the zone for you to get you started.
Midi games tunes can sound extremely good IF you have a soundbalster live! or similar card where you can load 8MB+ sound fonts. The quality of the instruments is very impressive.
On a mobile phone however, I think they're going to stink!
Still, for the sake of nostalgia.............