Bard's Tale trilogy (on C64), SSI Gold Box AD&D games (Pool of Radiance, Curse of the Azure Bonds, etc), Eye of the Beholder trilogy, Doom (and Doom II, but the original is better), Commander Keen series, Descent series (again, the original is the best), and a large collection of others
Edit: and I forgot Lands of Lore
Compare that to more modern games that I've actually been able to get into and play through:
Half-life, Half-life 2, Neverwinter Nights (played through then got rid of it), Civilization 3, Hoverace, and that's about all. Everything else I tried and deleted.