As a note I haven't seen every studio ghibli movie, ghost in the shell, etc.
1: The most important thing is a strong sense of being aesthetically pleasing. All the animals have a fine balance of realistic anatomy, vivid color palettes, and move in a way that is believable as animals, and have very humanlike emotions with the facial expressions and body movement.
2: like most Disney renaissance era films the animation is very smooth and lifelike. There's also a good sense of realistic physics with the way their bodies move. Most of it looks very natural.
3: what most disney renaissance era movies don't. Proper shading. It helps create an environment that feels so real.
3: particle effects! Most noticable during be prepared, the stampede scene, and the battle for pride rock.
5: a lot of scenes feel like they used real camerawork. Which is very impressive for a 2D movie. It's much easier to do in live action or cgi. The way angles change, the way it feels like the camera is moving, etc. not an easy feat.
6: the backgrounds are jaw droppingly good. The most impressive being the jungle in the second half of the film.
7: the choreography during the action sequences, like mufasa saving simba, the chase during the elephant graveyard, etc are coherent, varied, and boast many of the things mentioned already.
8: Even though the wildebeast stampede was cgi it doesn't feel that way, blending in with the hand drawn seamlessly.
Agree? Disagree?