Youtube has not everything
Legend of Kyrandia 1 and 2 had great music, I agree.
Here one can listen to (and download) MIDI music saved in OGG format from the first game and some other games, too - in clear Roland MT-32 + Sound Canvas quality, which is high above the simple Soundblaster OPL quality ingame.
Some other favourites of mine are:
Mechwarrior II (and Ghost Bear's Legacy Addon)
Alien Trilogy
System Shock (sounds even better with Sound Canvas)
Ultima VIII
Yendorian Tales Book I Chapter 2 (quite good music there though pretty short each)
Betrayal at Krondor (only the CD audio music, MIDI isn't as good)
Hexen II &
Portal of Praevus mission pack (both my
Nr. 1 favourites of all)
Fallout (anyone remember the awesome music from
The Glow?)
Fallout 2, mostly re-uses music from the first game anyway, except the strong (available ingame only with F2 Restoration Project)
track from Sulik's Village
Heroes of Might & Magic II
The Elder Scrolls 2 - Daggerfall (better examples linked by MrFlibble though)
Stonekeep (of course in Roland Sound Canvas quality, absolutely awesome there)
I could go on... and I like all and each one of them
