Why It Rocks
Extremely artistic and realistic animation.
Great development for every character. Every character is memorable.
Thumper is a great comic relief.
It spans from funny scenes to heartbreaking scenes (like the death of Bambi's mother) to thrilling scenes (like the forest on fire) with ease and without shoehorning them. The merit of this goes in part to the novel.
It teaches us men to respect nature.
The villain of the film, known as "Man" is very scary but he never appears on screen, which adds to the creepiness. The script and the plot make you hate the villain with passion, then at some point, you realize the villain...is a member of your own species.
It has a motivational soundtrack.
Great voice acting.
The Follow-Up is good too.
The Only Bad Quality
The Hunter Dogs can be creepy for some (even though it is a fairly old movie), not only because of their scary appearance or how they try to attack Faline, but because there's a gray dog in one scene who looks so scary, that his eyes look completely black.
Trivia
The chipmunk and the squirrel who make a brief appearance in the film were intended to originally have a major role and are a nod to Laurel and Hardy.
Paul McCartney claimed that he started caring for animal rights after he saw the scene where Bambi's mother gets killed off-screen by the hunter.
The creepy music that accompanies the Man is of three notes only.
Disney specifically stressed about animating the deers better, more realistic way than in Snow White and the Seven Dwarves. Eric Larson, animator at Disney Studios, claimed that the deers in Snow White were animated "like big flour sacks".
During the Hunter Dog scene, some of the dogs were originally given one spoken line which was "You can't escape from him even though you escaped us", after Bambi got shot, but Walt Disney took out the line because he thought it was too faithful to the book.