What makes Empire great, in my opinion, are two things... (1) yoda, who is a fantastically-conceived character, and (2) the buildup to Han being frozen in carbonite. The rest of the movie is, in my opinion, inferior to Star Wars. It's also a more claustrophobic movie, with everything taking place in cramped settings, whereas SW seems expansive. I consider SW the much better, much more great-by-general-standards movie. But Empire is very cool, and hard core fans tend to think that its gloominess makes it more sophisticated.