I don't beleive in absoulute 10 out of 10 games because no game that I think is perfect will stay perfect or be viewed as perfect in other people's opinions. The closest to perfect...Halo 3 because it's story is original(first Halo game I played), the music is outstanding, and the vast number of awesome multiplayer modes like forge, the different slayers, and everything in the double exp weekend. Half Life 2 is another candidate because once again it's story is original and interesting, the variety of cool guns and enemies is superb, and the characters are realistic and well designed. Oh, I almost forgot Paper Mario: The Thousand Year Door! Seriously, go play this game, its arguably the best game on the gamecube, it has some of the best characters and character diologue in gaming history, and it's extremely fun (for a JRPG). I'm going to keep looking at this thread because I really want to see people put their opinion with valid arguments. That way I can find lots of really fun games I never played.
EDIT: Damn! I forgot Portal! Well there goes my ``there is no such thing as a perfect game`` rant.