No Nemo is terrible because the Dori character is incredibly annoying and it fails as a comic device (especially after multiple viewings, I seriously wanted a mice and men ending for her character), I would rather the director and story have spent more time in the aquarium.
Having watched each one MULTIPLE TIMES (I have a 3 yo).
Cars (Because the soundtrack is good, the visuals are slick and in 1080p it is the best looking with all the reflective surfaces and simulated lighting) Also, the fact that they were able to create a kids story with a Pyrrhic victory and still have likable characters that are multidimensional and "grow" is amazing. Granted this is on the sophisticated side for kids and the typical American movie narrative, where the Hero has to win for closure.
I am looking forward to the Sequel. However, most kids I know really enjoy it, even if the main-character is intentionally unlikeable in the beginning.
Ratatouille (A Cyrano de Bergerac tale, with cooking/food as the muse- awesome) Great visuals, style and soundtrack. It captures the working restaurant atmosphere very well. Also holds up well for multiple viewings, again probably on the complex side for the "general public" but kids get it no problem.
Wall-E (close to a tie for second but, it suffers major diminishing returns with multiple viewings and has a weaker soundtrack- Plus, kids lose interest in this one more sit throughs quickly) It has a moral that is definitely on the preachy and beat you over the head with it side.
Toy Story (well balanced all the way around).
Incredibles, solid but definately for older kids/ weak soundtrack and smudgy visuals and textures (I get the style but I just don't like it).
Monsters Inc. Solid comedy, weak story. Kids and adults are mixed in opinions.
Bugs Life: Come on, the divided we stand AS INDIVIDUALS not as a mindless 'whole' moral, fantastic. Visual style is great but the soundtrack is on the weaker side. It certainly needed more comedy, but the canon-ball run style credit-roll outtakes are hillarious.
Toy Story 2
Finding Nemo, at the bottom, because a lost "Babe" story is too emotionally easy and for the reasons mentioned above.
Anyone who says ANTZ was better than Bug's Life needs to watch PBS kids shows for days on end Clockwork Orange Style (strike that, they would probably enjoy it.