Oh gosh. This is tough. In no particular order:
Diablo 2
The Longest Journey
King's Quest VII
The Curse of Monkey Island
Grim Fandango
Oblivion
Baldur's Gate
Baldur's Gate II
Chronotrigger
Secret of Mana
Terranigma
Quest for Glory series
Super Mario Galaxy
The Sims
Princess Maker 2
Runaway
Portal
Gabriel Knight 1
I don't know if these are even my absolute favorites, but they are some darned good games.
