I voted Bug’s Life, there just wasn’t a connection with me when I watched it, plus it’s the only Pixar movie I’ve seen less than 10 times 
Now I’m able to reply.
My least favorite is The Incredibles. I didn’t like it at all. nothing impressive for me, no moral, just a wow-wow-cool-action 
Then, I do not understand why you bash Cars. It is my #2 fav cartoon (and movie, by the way). TS2 is #1 now, Walle is kinda #3. Actually, I can’t say that, because these three numbers are too blended… I have seen Walle too many times, so it lost its interest.
Then, after this trinity Ratatouille, Monsters Inc and TS come. After that - Finding Nemo, A Bug’s Life and far in the end - The Incredibles.
Actine: Hmm, I can disagree with you about no moral from the Incredibles. I knew there was one.
Ratatouille and A Bug’s Life are probably my least favorites, followed by The Incredibles. All three are alright films, they just didn’t wow me like WALL-E and Monsters, Inc. did.
ABL is my least favorite. Although it IS NOT bad it’s just not as good as the rest of the pixar movies.[/i]