Life.. Hurrr. Not really. Uh, the best game I've played would probably be.. Diablo II. Yeah, that's right. CLIKAN GAEMS. Not so much the constant clicking,armor, and hacked characters, but the memories of me and my friends spending up all night on a good ol' LAN connection. Using energy drinks to keep us awake, and then be completely immobile the next day. Ah, good times.
Holy crap, Sy! Those are ooooold! Still good though, personally, I would KILL for an old copy of LoZ: A Link To The Past. But my favorite (at the moment) would have to be ahh...ahhh... Garry's Mod ? Ehh, I don't really know.
I don't really have a favorite game. I'd say my favs are in series. Mine is the Legend of Zelda series and the Metroid series (scratching the first one and last one made) and soon D3 and Too Human might take a place in the list. Damn, so many good games coming out.