According to RottenTomatoes and IGN these are the best rated animated movies ever. I don't know why Spirited Away, which is rated higher than some of these ON RottenTomatoes.com isn't on the list.
Overall its a decent list, but I don't think EVERY single Pixar film needs to be on the list, and obviously Spirited Away should be on the list. Also, Grave of the Fireflies should probably be too. Tripletes of Belleville is another one that actually is rated higher than Lady and the Tramp, but was still omitted. And I like Toy Stories (though I prefer 1 to 2), but taking #1 and #2 is a bit too much.
On a final note, I am proud of myself for owning all of these (except the not yet released Persepolis!Anyone want to borrow one?
Anyways, without further ado, here is the list.
25. Lady and the Tramp
24. A Bug's Life
23. The Cat Returns
22. The Lion King
21. Beauty and the Beast
20. My Neighbor Totoro
19. Princess Mononoke
17. Monsters, Inc.
16. Wallace & Gromit: The Curse of the Were-Rabbit
13. One Hundred and One Dalmations
11. The Nightmare Before Christmas
10. The Iron Giant
9. The Incredibles
8. Finding Nemo
7. The Secret of NIMH
6. Kiki's Delivery Service
5. Kirikou and the Sorceress
3. Snow White and the Seven Dwarfs
2. Toy Story
1. Toy Story 2
EDIT: I guess Cars isn't on the list, but it is better than A Bug's Life