Ok, my top 5 that probably haven't been mentioned so far.
There was a PD platform game called Quick and Silver, which I thought had a really great themetune, I would let it play over and over and over and over, it was pretty long! :-D
Also I loved the theme tune to Datastorm, a game that came as part of a bundled pack of 10 games in the Amiga Magic pack - A500 ... from Gordon Harwood computers. ... not sure how else it was distributed but I LOVE that game and the themetune was really cool. (defender clone) :-D
Astro Marine Corps was a pretty cool platformer that I liked.
Hmm .. well I am not remembering too many other tunes at the moment . . I of course loved SOTB 1&2, superfrog, etc.