ESB has several things that reduce its stature as a “great” standalone film. The dialog on Hoth is weak. The effects are sometimes gratuitous and border on cheesy (Cloud City, Obiwan force ghost), the Leia love triangle is sometimes strained. Many things happen that have little or nothing to do with the story (the asteroid creature, Luke getting lost in the snow). The whole movie is clearly an “installment”, without beginning or ending (not that movies necessarily need that, but movies of this genre generally do). Much of the film is claustrophobic and takes place in enclosed areas rather than in large expansive areas. In my opinion, the effects (with the exception of Yoda) don’t hold up as well as those in Star Wars.

What makes ESB great is: (1) Yoda, and (2) the two climactic scenes at the end (Han/Leia/carbonite, and the lightsabre battle). The rest of the movie is an exciting chase.