In short, it's regarded highly because it's a Kubrick film. Essentially that means the movie was micromanaged and shot, and reshot until it was absolutely perfect. Kubrick just has this way with making stunning shots. The cinematography in this movie is just outrageously incredible. Every shot and angle has meaning, every scene is powerful and moving. In my mind (of the movies I've seen so far) the only movie to make better use of the camera as its own character is Citizen Kane. It's just an excellent demonstration of why I love Kubrick so f***ing much.