Most of the amiga examples:
Ultima, classic themes
Druid2 (Fairlight) I still play that one now and then..not sure where the nostalgia ends and the tune begins.
Lemmings, i like the taxing lev 1 tune, (the only original tune?) but all of them together makes it stand out.
Battlesquadron, the essential chip+synth hybrid
Mario bros, anyone who doesn't love super mario bros?
Daytona, daaayytooonaaa.. ok, it's more fun then good.
Homeworld 2, this one should have silenced all the "debate" about "CD games" killing good music.
Baldurs gate 2, the same composer has made a lot of great game music.