Neither the best, nor the most critically-acclaimed, but your all-time personal favorite.
For me, it'd probably have to be Treasure Planet. The level of imagination they put into the art, character, and prop designs is amazing, even by Disney standards; and it added just enough twists to the original story to to be creative in its own right. Reading the book a few years later, I transplanted the depictions of the characters into the story playing in my mind. In retrospect, I'd venture to say it was the best novel I've ever read.
I also played the PC game Battle at Procyon; a sort of semi-official sequel to the film. Though I never finished it, it was surprisingly good due to being made by the same guys behind Homeworld: Cataclysm.