Its interesting that most of you have talked about just games music. To me some of the best amgia musiv wa sin demos...
Global Trash by The Silents was awsome
There was a demo Called COMA by the rebels which is superb
and the into music on the red Sector Mega Demo
thats just to name a few
...but if you want a game with greate music, Eliminator !!!! try playing that through a modern amp !!!!