I liked the earlier Don Bluth stuff a lot, like the Secret of Nimh, the original Land Before Time, etc., even though I haven't seen them since I was a kid. I enjoyed Anastasia, too, although the animation style for DB stuff is perplexing to me; almost rotoscoped with just enough exaggeration and bounciness to mess with my head.
I always loved the classic Disney stuff like Sleeping Beauty, was in love with the Little Mermaid when it came out, along with most of the "second wave" Disney stuff from that time (except the Lion King, I never really liked that one). I have a major, major soft spot for Hercules, since I'm a total Greeknerd, and I loved The Emperor's New Groove for a lot of reasons but mainly because it was really nice to see them try something different for a change. I also really liked Lilo and Stitch for a lot of the same reasons.
I absolutely adore the Incredibles, I saw it 5 times in the theater, which is unheard of for me anymore. Also the Iron Giant is one of my long-standing favorites. Of course the Miyazaki stuff has to go in there, Princess Mononoke in particular (I was disappointed in Howl's Moving Castle, though). I also really liked the Triplets of Bellville, for anyone who missed that when it came out, and the Nightmare Before Christmas was a long-standing favorite, too. Who Framed Roger Rabbit is still up there, too.
As far as least favorite, the cheap-quels by Disney and Don Bluth (Land Before Time 5 billion, anyone?), and I have honestly never cared for Snow White, even when I was a kid. I understand its importance and how ground breaking it was, but the film itself really never did anything for me. And I have to put Cool World in here, 'cause that was just a stinky pile of cheese if I ever saw one.
Oh! And I LOVED the Rankin-Bass stuff from the 70s and 80s! The Hobbit and Flight of Dragons in particular (I watched that second one so much when I was a kid my parents finally forbade me from renting it anymore). I saw the Last Unicorn, but there was swearing and harpy boobies in it, which freaked me out. But yeah, I still love those.