Portal (because it's freakin' portal, duh)
Dark Cloud 2 I don't really know why, but I just really fell in love with this game, it's mechanics, aesthetics, and especially it's story just drew me in)
Okami(I've always had a fondness for wolves, and that's what led me to pick up this game, but the art style and the fun of doodling with the brush kept me playing)
Legend of Zelda: Ocarina of Time (Who doesn't love this game, honestly? In fact, the reboot of this may be the only reason that I get a 3DS. Why they didn't wait and release it when this and a couple other big games were ready, I'll never know)
Assassin's Creed 2 (I'd vote for the whole franchise if I could, but the other 4 need votes too, so I picked AC2 because it fixed a lot of problems from AC1 and AC:B was really just a big expansion pack, a good one, but an expansion nonetheless. So AC2 is the best of the 3 imo)
EDIT: can we have a separate list where we can vote on franchises/series as a whole? Just franchises/series though, I'd say 2 or 3 votes a person, and only games that have at least 1 sequel and different consoles or non-game merchandise do not a franchise/series make, at least not by themselves.
EDIT2: Wow, I made it on the first page of what will probably be a popular thread... this has never happened before... kinda awesome
