The problem is the original 3 were the new era of movies, now everyone expects the new 3 to push the same envelope but it is impossible, also there is a limited story to work on considering Lucas had this planed for a long time and there is a dam huge Star Wars universe out there, so he couldn't just make up the main story. Also the reason Lucas done the original 3 was because that is what he beleived to be the best and strongest story(right in the middle of the action), so if Star Wars did flop then he would have released the most user freindly part of it and would not have been left woundering if he should have told the story differently.
So yeah there will be people who say that the first 3 are the best but George Lucas knew that and now he is telling the first part of the story which in normaly more info so more boring.