Up grabbed me by the emotions and never let go. If I'd been alone while watching that movie, I would have cried, laughed, and whooped my way to insanity; luckily, self-restrain kept my wits at arm-length. There was just so much I liked about it, I can't really see how any of the other films could be better.
That said, Wall-E was absolutely amazing during the parts where no one talked. The part that I have the most against, and perhaps I didn't properly understand it, was the part where Wall-E proposes to complete the directive so he could repair himself. I liked how EVE gave up her life for WALL-E, but the fact that in the end, he just wanted to get some repairs just didn't feel right. And, as my sister says, it was a bit political.
I regard Toy Story as a single entity, and as such, it takes third place for investigating real issues and real characters in a setting that was both imaginative and unique.
Then comes Incredibles, Monsters Inc., Ratatouille, and Finding Nemo, in that order. Not much to say here, they were all good movies, but Pixar has a high bar to reach.
Brave and Cars can go sit in a corner and think about what they've done.
EDIT: I forgot A Bug's Life. I suppose the omission speaks for itself.