So many things that come together to make a brilliant and memorable film
The storyline itself is very dramatic and appealing
The characters are just brilliantly done, in their art, but especially their voices. (JEJ and Jeremy Irons especially <3)
The comedy is amazing for a disney film! It's not just captain hook getting chased by an alligator, or a pointless fall where dishes and stuff come crashing down, it's actual jokes with adult layers to them. =)
The animation is very impressive, and beautiful
Bu the lasting impression for me comes from the music
There are <very> few disney songs with the same power and energy as any song in TLK, and TLK has a stunning five plus instrumental music. That's definitely what sets it apart from all other movies in my opinion <3