I had to sit on this one for a bit and think about it. I think a simple answer might be The Last Unicorn. I watched that one a bunch growing up, later read the book and it has always had a fond place in my heart. The first two pokemon movies are p good imo. Oh, and a close runner up might be treasure planet I actually quite liked that one, I had previously read Treasure Island. I should rewatch all of these sometime.