Arbitrarily...

Because John Scalzi did it, here's my ranking of Pixar films, from best to worst.  Cars 2 and Toy Story 3 are omitted because I haven't seen them.

1. The Incredibles

2. Wall-E

3. Up

4.  Finding Nemo

5. Toy Story

6.  Brave

7. Toy Story 2

8. Ratatouille

9. Monsters, Inc.

10. A Bug's Life

11. Cars

I commented to his post with a slightly different list, but I keep fidgeting with it the longer I look at it.  Anyway, the top 8 are all fantastic films.  Most people like both Ratatouille and Monsters, Inc. significantly more than I do, but I never connected all that much with either.