I did a research paper on the evolution of video game music last year, so I know a little about it. The best are those in the most memorable games, and listening to the music will bring back a flood of memories of hours of button mashing and frustration

There are some great MIDI files out there - I suggest the following:
http://www.vgmusic.com/http://laurasmidiheaven.com/VideoGms.shtmlIf you need more, just google for it. These sites will remind you of all the great music out there, the next step would be finding instrumental recordings of them, or seeing if someone at your college's music comp. program would arrange them for instruments, and then seeing if anybody would be interested in performing them, you'd be surprized at how many musicians would like to play video game music.
If you want to progress past the simple music in the older systems, though I don't know why, then you get to much more complex music that was stored on CD's, and was sometimes already instrumental. I have a CD of Grandia II music, which is decent. I also like the music in many of Black Isle's games, it had good transitions, strong melodies, and well used harmonic progressions. If you need any more information, I'd be happy to do some research.