The first film in any series seems to always be considered "the best" by viewers, but why?  Because the characters are all new.  As an audience, we're just meeting them for the first time, which makes all characters interesting.  The problem with sequels is:  How do you keep them interesting?

Ocean's Thirteen delivers...in spades.  New villains to loathe.  New cons to plan.  Old villains to thumb our noses at.  In the series so far, I like 13 the best.  The gang is smooth, in their Vegas Cool-style, and three movies in, we're still learning more about each character.