1 The Elder Scrolls - Arena - I almost said Daggerfall, but Arena really was the game that made me a pc gamer (instead of just dabbling with them on school computers)
2. Baldur's Gate 2 - I'd love to nominate all of the bioware dnd games, but BG2 was my favorite.
3. Quake - if I can add the team fortress mod. I played many many hours of Quake tf. I played some ctf too, as well as death match. But, my clan was team fortress based, and thats what I liked the most.
And I'd like to nominate Everquest as my most loved AND hated game ever. I'd dabbled with some muds and ultima online before eq. But, I was extremely addicted to eq for many, many years. It's the game that broke me of ever being serious about another mmorpg ever again (although I'll dabble with just about any of them now). Just thinking of playing Eq again makes me want to hurl just a little.