We all enjoyed the prequels but most of us agree that the movies are not as strong as the originals. Because Episode III is going to be the last Star Wars movie EVER, we all want it to be the best!
Episodes 1 and 2 were full of weak points, errors, plot holes, etc. If George decides to research what fans thought was weak in the movies and correct them it will probably make the 3rd movie a hell-of-alot better. What mistakes where in Episodes 1 and 2 (and the OT?) that should be improved on for Episode 3?
I think Lucas' BIGGEST problem in the PT is that he's more focused on Special Effects and action sequences. He should focus more of the story! Instead of writing the story and putting in what will fit, he tries to add these massive effects/action sequences that top the last movie, but we don't need them!
I also think he should cut down on the CGI. I think CG works for locations and ships, but for living creatures (such as the Geonosians) it is too obvious that they are not real. Puppets worked FINE, and also gave the actors something to interact with. I think Lucas has jumped straight into the CG without perfecting it first. IMO the OT looks ALOT more realistic than the PT.