Hopefully I'm not necro'ing this thread.
1. UFO: Enemy Unknown [DOS] Easily the greatest game ever. Strategy, Action, Terror, and truly overwhelming odds add up to an amazing package.
2. Fire Emblem: Geneaology of the Holy War (Fire Emblem 4) [SNES] Fire Emblem is great, and number 4 is the best. (The one released in the West on the GBA as 'Fire Emblem', is in fact, Fire Emblem 7, in case you didn't know)
3. Super Mario 64 [N64] Still truly epic. Sunshine was lacklustre in comparison. We can only hope Galaxy will be as good.
4. Millenium 2.2 [Atari ST] Another genius game, long forgotten.
5. Zelda: Twilight Princess [Wii] A tough call; but for me, TP was very much a worthy successor to Ocarina.
6. Blood [DOS] Still my favourite FPS of all time. Camp humour, gratuitous violence, funny weapons, insane cultists; what more could want?
7. Burnout 3: Takedown [PS2] Still the best burnout. Revenge was pants. Who doesn't like driving like a lunatic and being rewarded for it?
8. Seiken Densetsu 3 [SNES] Best Secret of Mana game, bar none. Plot a little thin, but the Class changing is perfection.
9. Super Smash Bros. Melee [Gamecube] Easily the best multiplayer game I've ever played.
10. Final Fantasy X [PS2] Yes, I know... 6 comes awfully close, but I still can't help loving X. Despite the angst and the gackt clones, it still gets my vote as the best FF. Besides, Blitzball is hilarious.
Ummhmm, Quite a selection there...