As good as Uncharted 2 is, Uncharted 3 takes it to the next level. I've yet to play the first one, though.
I would put Uncharted 1 as a solid 6.5 out of 10. Good game, good story, but things get bogged down in the gameplay. Every fight sequence is longer than it should be and things get repetitive. To extend on the parallel from my earlier post, I'd put Assassin's Creed 1 at a 7... only better than UC 1 because of the story.
To me UC2 and AC2 are both 9.5 type games. Not perfect but darn close. If AC2 had the chain kill fight technique of AC-B and AC-R, it would be the perfect game in my mind. UC couldn't get to 10 for me unless it became open world with multiple side missions and challenges.