Mainly because it wasn't more of the same. I think it continued the story in a logical way. If you blow up the Death Star, you do not win for good, The Empire will come after you. It tells you what happens afterwards it isn't just Episode 4 with same characters, different villain. It is a logical continuation and I think it is the one of the greatest movies ever made. Granted, I like the first one a lot but I think this one is definitely my favorite but I guess that is just my preference.