I too was a Star Wars fan like most other young people in the 1990s. The original trilogy had it all: relatable characters, frightening villains, high fantasy, and exciting battles. I've never watched Star Trek or read any of the Star Wars books; my only connection to science-fiction is through the Star Wars movies. What made those movies so enjoyable was the fact that they were "good" movies. From a film-making standpoint they earned high marks. The characters were especially strong. They were archetypal in a good way. Lucas (and the rest of the team) took familiar tropes and placed them in a fantastical universe. Luke was the reluctant hero who discovered himself in the process of the story. Darth Vader was the hero-turned-villain who ended up sacrificing himself for his son. Han Solo was the rogue with a heart of gold. Etc, etc.
Comparing the characters of the original trilogy to the prequels is just saddening. The villains are one-dimensional; the heroes boring. There is no depth to a Mace Windu or even an Obi-Wan. They are exactly who they appear to be. There is no discovering, no showing. Lucas tells us who they are. We don't see Anakin and Obi-Wan's friendship develop on screen. We hear it exists. We hear that they had some incredible adventures. But we never see it. Plus, there is no chemistry between Ewan Macgregor and Hayden Christensen. This leads to another key point: there is no true (i.e. relatable) protagonist. Obi-Wan is too distant, Anakin is too annoying, and Padme lacks more than one dimension. Luke was clearly the protagonist, and he evolved in each movie. The prequels lack that.
The storytelling, action sequences, and general direction of the plot are all quite weak as well. But it all stems from the characters. At the end of Episode III, the audience should be screaming "NOOOO!!!!" when Anakin becomes Darth Vader. Instead, many thought "good riddance. That's what we came for, right?" This makes it clear to me that Lucas was chiefly focused on shoving as much CGI into each scene as possible to please younger fans. I'll admit that when I first saw the prequels I liked them. After all, I was young and the movies were "cool." People like me bought the toys, games, and various other merchandise that Lucas designed the films for.
So, enough complaining. Time to think proactively. How can the prequels be salvaged? Well, to start with there needs to be a real change in who's in charge. Lucas is going to be a part of the process; no changing that. But his role can be limited. Since this is an alternate history website, let's say that Steven Spielberg offers to direct the movies. Lucas agrees. He stays on to be executive producer and churns out the first draft of the script. Spielberg reads it, notices the clear problems, and proposes that a team of professional script-writers are brought on to make some changes. Lucas accepts. He will still have final say on whether or not the changes are adopted, but I can't see him rejecting improvements. I believe that Lucas wrote what he did because simply believed it was the best script he could write. Some people aren't great fiction writers. If a better script was left on his doorstep, while still including the crucial elements, I believe Lucas would have accepted it. I also believe that no one in the production team for the prequels had the nerve or willingness to present a better script, or to challenge Lucas on anything. Spielberg could have done that, and if he had directed the prequels they would have been much better.
P.S.: A lot of credit goes to Red Letter Media for helping zero-in on the core problems with the prequels. I'm not a film-maker or film-student. They are.
I think people forget what some of George Lucas's original ideas were like. Some of the good things in the original movies were there because Lucas lacked the budget and power to get away with doing what he wanted.
The best thing about the first movie was that young kids could relate to Luke Skywalker. They thought 'I could be him'. But Lucas originally conceived him as a predestined Jesus type figure (which he did with Annakin later).
On balance I think Lucas was lucky to get away with Star Wars. He could have ruined it on day one but luckily he was unable to do it due to people like Harrison Ford fighting his awful dialogue and the heavyweight acting skill of Alec Guiness.