I liked about 90% of Pixar's movies until Up. (I know everyone loves that movie, I didn't).
Here's how they rank in my skewed opinion:
Toy Story: 10/10 (Considering it was their first, it was very groundbreaking in animation and story for a children's film)
Bug's Life: 7/10 I loved it as a kid, but it doesn't hold up well, and their were some dumb parts.
Toy Story 2: 10/10 It somehow held up to the original, and added to it
Monster's Inc: 9/10 Really awesome idea, and followed through pretty well. Overall great movie.
Finding Nemo: 7/10 I know it's considered a good movie, but I had to try and watch it 3 times before I finished it. Nothing attracted me to it, and I HATED Dori.
The Incredibles: 10/10 My favorite Pixar movie
Cars: 4/10 I just thought the whole premise was stupid, and couldn't suspend my disbelief enough to enjoy or get engaged with the characters
Ratatouille: 8/10 Loved that movie! I think it had some pacing issues and some generic, easily seen character building, but overall very enjoyable.
WALLE: 8/10 Most of my friends hated this movie, but I really enjoyed it. I thought the way they made this was very unique, and inspiring.
Up: 5/10 Sorry just didn't enjoy it. I thought the 10 minute intro with the sad story of the guy and his wife was better than the rest of the movie. I hated those talking dogs.
Toy Story 3: 10/10 How the hell did they do it again?? I was shocked by how good this was.
Cars 2: N/A Didn't waste my money
Brave: 5/10 This seemed more like a generic Dreamworks movie than a Pixar film. Wasn't terribly offensive, but definitely nothing special about it.
Monster's University: N/A didn't see it.
Inside Out: 9/10 Felt like a return to form! Made me cry in the theater.