3rd world income being what it is, I don't own as many games as the rest of you.
But I do pick them very carefully. Here's the ones I can remember :
Space Quest IV (unplayed)
Space Quest VI (The Spinal Frontier)
Red Alert + Aftermath (unfinished)
Panzer General
Pacific General (unfinished)
Fantasy General
X-Com : Apocalypse
Alien Legacy (unplayed)
Settlers III (unfinished)
Settlers IV (unplayed)
Master of Orion
Master of Orion II
Master of Magic
Alpha Centauri
Space Empires IV Gold
Diablo (unfinished)
Lands of Lore
Shellshock (unfinished)
Emperor of the Fading Suns
X-Wing Alliance (Atrocities, get this one if you can !!)
Rogue Squadron (unplayed)
Bureau 13 (unfinished)
Free games :
Angband
Nethack
ADOM
I'll update this list when I get home. I know I have a bunch of old games I got for $3-5 each and haven't tried out yet.