In my opinion, Commodore 64 games had the best music out of all my systems. Like to me, they had a unique sound to it.

I have a couple (in no particular order)

Last Ninja 1 & 2
Nemesis the Warlock
Main Frame
Zak McKracken and the Alienminders
Maniac Mansion
Draconus
Commando
IK + (which I thought was International Karate )
Grand Monster Slam

and a bunch of others.