Why are MP3s the only selection available? Older systems could use Midi sound just as good and take a fraction of the space.

[Fugus]

Noticed that when looking at the Super Nintendo Music, that whole collection leads to being HUGE.

But you could put them in midi format and they would sound just as good and a 3 to 4 minute midi will be a few kb as compared to an MP3.
Save the MP3s for stuff that wasn't midi to start with IMO, some emulators back in the day even let you dump the midi files from the roms if I remember correctly.