While some may be critics Star Wars merely because the series had so much hype, the reality is there has never been any other set of movies like these. Lucas, working independly of studio control, is able to see that his projects are as he envisioned them without compromise.
I had to see Episode III twice to soak it in. A lot happens in this film. I almost wished the film was twice as long. More stuff occurs in this film than the two previous combined.
Personally I liked Episode I and II. Ironically, I actually had some issues with III. I think it would have been more effective that Darth Sidius only revealed himself to Anakin after he had already been his student for a while. Generally it takes longer to tell the story of someone going bad than the inverse. Anakin's descent seems rapid and I had to pounder how realistic it was. Mind you, if you pay closer attention to Episode II you can see the seeds of his undoing.
I have to agree with Ebert and Roeper that the weak spot in this film (as well as others in the series) is the dialogue. Someone other than Lucas should have directed. He had too much to focus on aside from the acting.
One thing about this film is that it makes scenes in Episode IV much more significant.
Is this really the end of the series? There was once talk of doing stories involving Han and Leia's offspring. The worst thing for Lucas to do is let someone else take over the series and kill it as was done with Jurassic Park and Aliens.
Lucas has created a universe onto itself, much as Rodenbury had done, which Rick Berman took over and made other series. It is conceivable that other movies set in the Star Wars universe could be made. After playing the fanstastic Star Wars caomputer game 'Knights of the Old Republic', I keep thinking that they would make an awesome basis for a film or films or at the very least an excellent 26-episode TV series.