My favorite is
101 Dalmatians. That's the first one I saw in a theatre (on the occasion of my 9th birthday).
But before that, I'd read the Big Little Book versions of Snow White, Sleeping Beauty, Cinderella, Pinocchio, and I had a Little Golden Book version of Bambi. I had the comic book version of Sleeping Beauty, too.
Snow White scared me so much that for awhile I wouldn't eat apples, and I had a nightmare that my dad's little Toyota got stuck in the corridors of the Wicked Queen's castle (I was 8 years old, okay?

). Because of the pictures in the Bambi book, I have never been able to finish reading it, nor have I been able to make myself watch the movie.
But I also love The Aristocats, Robin Hood, Fantasia, The Rescuers, Little Mermaid, Lady and the Tramp, and Peter Pan.