Fantasia will always be my favorite for its sheer innovation. It's sublime blending of animation and classical music was years ahead of its time and lifted animation from light-hearted entertainment to a serious art form. One classic segment follows another, from the lyrical whimsy of the Nutcracker Suite, to the daft silliness of Dance of the Hours, to the profound drama of Night on Bald Mountain/Ave Maria.
Despite a cool initial reception by moviegoers and critics, Fantasia remained the animated film Walt was most proud of. It literally took decades for it to find its audience, but now, more than 60 years after being released, it stands head and shoulders above all Disney films and is the standard all animated films can only aspire to.