I’ll be brief on this one since this is one of those cases where a picture says 1000 words.
If I were to judge this on story alone, I would not have liked it. But everything else is so much better than that. The voice performances are fantastic, the songs are memorable, and the villains is one of the best to have ever appeared in cinema. But the thing that makes this one of the best animated movies of all time is the animation. More than 50 years after its release, it remains the most beautifully animated movie ever. Guillermo Del Toro has cited it as being one of the movies that influenced him the most, for the animation alone. Anyways, like I said, pictures say more than I can write about this one