As I read through all these posts and try to come up with my answer, what's astonishing to me is the lack of turkeys in the Pixar canon. I can't think of any instance where critical and audience acclaim wasn't extremely high. They are ALL GREAT. And damn if I can't come up with my favorite. Unlike every other celebrated director in my personal favorites lists, It seems I can sit down in front of any new Pixar film and be guaranteed that I (and my kids) will be thoroughly and completely engaged and entertained, from Toy Story onward.
The directors of Pixar films always get to play the best parts, too (Andrew Stanton as Crush the Turtle, Brad Bird as Edna Mode).
They also know when NOT to make a sequel...I can't believe there was wisdom enough to let Monsters Inc and Nemo stand by themselves (hopefully...fingers crossed)
If pushed, Monsters Inc and Nemo. And The Incredibles. And Toy Story. And WALL-E. And Ratatouille. And UP just slayed me. And Toy Story II is as good a sequel as Godfather II.
(Uggh...that's enough sunshine for today...time to reset my brain with some Antonioni, probably The Passenger).