Haven't gotten around to 13 yet, but 11 and 12 are equal in quality, but they work in their own special ways. 11 works so well because of Danny and Rusty (I would kill to have a freindship like theirs), the inventive editing, the actual heist itself, the suspense and danger, and that great first ending against the fountain. The one thing I feel that does hurt it though is the epilogue thing with Danny and Rusty and Tess. I feel like if it just ended with the characters walking away from the mountain, especially with that gorgeous music.
Ocean's 12 works well simply because it doesn't take itself remotely seriously and is so gloriously self-indulgent. I just like seeing these characters go around Amsterdam. I like seeing Catherine Zeta-Jones as the snooping detective trying to hunt them down. I like Tess pretending to be Julia Roberts in a weird meta angle. I like that Bruce Willis is just...there. I love how many weird twists are in there.
O11 works as a good standard heist film, while O12 is just a wild, good time.
Why didn't Steven Soderbergh do this movie again?