If I had to pick the best one from several of my main choices, it would have to be the fact that TLK is the exception to Disney. I'm not really a Disney itself fanatic. But let me just say that (and since I was born a couple of years before 1994), TLK apparently did raise the standards of how the world views traditionally animated movies. This includes the characters as well.
I think I should note that the music itself is powerful in this movie. Moreover, the scores in my opinion.
The scenery is another area to note as well. I think this is the most artistic area of the movie. I mean, the scenes of the savanna and the rain shafts that show up (leading to the nocturnal storm with lightning strikes going on nearby Rafiki's tree) I think, is amazing to see visually in traditional animation.