You missed a few; ratatouille, the incredibles, Fining nemo and Monsters inc. you forgot. or did you not see them? BTW, Pixar is making a sequel to Monsters inc, it's called Monsters University. I don't know if it will match up to the original without Pete Docter, but I digress
Anyway, here's my list (I am not including Cars 2 because I have not seen it yet):
1: Cars (I love cars, and thus I love Cars. The touching story and lovable characters don't hurt, either)
2:Wall-E (A robotic romantic comedy with subliminal messages about the environment and obesity. What's not to like, even if it borrows from other movies (cough cough short circuit cough) ?)
3: Finding Nemo: (I loved this when I was younger, and I still do. These life messages are not so subliminal, and the comedy keeps the story rolling. I love andrew stanton!)
4:Toy Story 3 (Memorable story and classic toys meeting many new. A must-see. I just have one question: what took you so long, Pixar?)
5:Toy Story 2 (10 times better than the original. Pixar started to mature as a company around this point, and TS2 shows it.)
6: Up (I sense a pattern of touching stories with pixar movies, and Up is no different. The creativity here is genious. The movie is a little stale in the beginning, though...)
7: Monsters Inc. (The only reason Monsters Inc. is #7 is because everything else is better. Monsters Inc is legendary, and it's no wonder that Pixar is making a sequel. Again, what took you so long?)
8: Ratatouille (The story doesn't flow well, although it has charm. Brad Bird could do better, but it's good as is, for the most part.)
9:Toy Story (Don't get me wrong, I love this movie. But Pixar could do a lot better animation- and story-wise. Pixar was still starting out, and this movie reflects that. I would have liked to see more, though.)
10: The Incredibles (See first sentance of #9. However, The Incredibles was over-hyped, and the story is a typical superhero-fare plot. While Toy Story and A Bug's Life have the exuse of being the first Pixar productions, this has no alibi.)
11: A Bug's Life (This is the only Pixar movie I don't like. I don't dislike it, it just never really got me into the story. It also seemed kind of rushed to me. It's still very good, though, just not good enough for Pixar's standards)