Well, it's late, but I will give it a shot in no particular order:
Warcraft II : I loved this one. Warcraft III was not as good. better graphics, but II was something else
Monkey Island series: Okay, I have a soft spot for Guybrush.
Elder Scrolls III: Morrowind. That is probably my favorite of all times. I have played it again and again. I loved it. I wish Oblivion was as good in story as Morrowind was. I hope Skyrim has a story like Morrowind, and the better graphics. I am so waiting for Skyrim, I have pre-ordered it.
I almost always play a woman. So it was really crazy when I had to be recognized as the Nerevarine, and went to get Dratha's approval... I always join House Telvanni, I love the crazy mages.
Command and Conquer Series: not the Red Alert ones, and up to Tiberian Sun. Have not played either generals nor anything after Tiberian Sun and its expansion.
Diablo : the original one. The second one had a stupid save system and I hated when saving and exiting getting back to the town and not at the spot where I saved. It's not like one can always do a whole level at one time!!! I hope Diablo III has a better save system if it ever comes out. We've been waiting for it for a couple of years now.
For old times' sake: The Sierra games: Space Quest series, Larry series, Police Quest, and everything else from Sierra that I am forgetting. I spent lots of hours playing those games.
Doom: yes the FPS that started it all. I have been playing Doom since it first came out as a DOS game.
And I am certain I am forgetting a lot of the good stuff.