Bambi
I've always been in love with the music and story of this film. It wasn't until I got the nice, cleaned up and restored version that I really appriciated the how pretty the film is as well. If you have the DVD, check out clips where they interview the animators...great stuff.
Also, props for Disney for not including the scene in the book where Bambi's dad tells him to bugger off while he enjoys a Springtime romp with Bambi's mother. That was odd.
Fantasia
Leopold conducting. Unicorns. Flying horses. Dinosaurs with Stravinksy. Huge honkin' deamon. Need I say more? I love
Fantasia 2000 just as much, just for including 'The Firebird Suite'.
Princess Mononokee
After years of getting annoyed by animie, this film actually made me a fan. I've gone on to watch most of Studio G's stuff, and I've enjoyed it all.
Sleeping Beauty
Yes, I picked three Disney movies. And for different reasons. What's always impressed me with Sleeping Beauty is the artwork. Because this was the jump to a larger screen size, backgrounds needed to be more detailed. Furthermore, there's a whole 'tapestry' look to the whole film that's unlike any other Disney film.
Plus, one brutal bitch of a dragon.
...I'm holding off on my fifth choice at the moment.
Watership Down comes to mind, because it was a British acid-trip of a movie, but NIMH comes close too...I haven't seen either movie in years.