Babel On, Babel Off: If *I* had Written it ...

Pretending for a moment that it's worth the time and brain-cycles to think about, the primary failing of Sith was the way they completely dropped the ball in convincingly motivating Annakin to jump to whole-heartedly to the Dark Side. There was no real inner conflict; no real moment of truth where Annakin had to make a heart-breaking choice.

Of course the whole Star Wars endeavour has always been too shallow and black and white. Stephanie Zacharek's review in Salon puts it well:

So is Palpatine supposed to be George W. Bush? It appears so, because he's ruthless, unappealing and arrogant. He's a cartoon baddie, like Ming the Merciless, or Mumbles, or the Penguin -- all of these are very bad men, just like that bad old George W. If Lucas really knew what he was doing, he'd have given us a character who believed with all his heart, as George W. surely does, that he's on God's side. That would have made for a truly creepy and treacherous villain.

But again, let's try to pretend that it's worth fixing: here are my main ideas for how I would have written Revenge of the Sith:

First of all, Lucas really lost his opportunity to delve deeper into this idea of the Prophecy and "Bringing Balance to the Force"? In what way is the Force "out of Balance"? (And how could Obi-Wan in the final moments of the duel say "you were the Chosen One: you were supposed to destroy the Sith, not join them!" -- since when was Bringing Balance to the Force supposed to mean "destroying the Sith" when everybody believed until a few years ago that the Sith were no more?) Lucas touched on it with Palpatine's lie: that you have to get to know both sides. He really could have done more with it, because in fact there is a lot that is wrong with the Jedi despite Lucas's desire to paint them as perfect and Perfectly Good.
Yoda's conversation with Annakin would have been a perfect launching point: Yoda's best advice to Annakin is to stop caring about his the person about whom he has had a vision that they are going to die. All very Buddhist, which I think is what Lucas is trying to evoke with his Jedi, but it's really not very satisfying.
The Jedi have been very ineffective in protecting the Galaxy from falling apart. Why do all these systems want to secede? See Jonathan Last's Case for Empire for more about this idea.)
Basically, we can see where this is all leading. The Jedi are these Celibate, detached, perhaps even a bit out-of-touch, passive and passionless "warrior monks". How can they possibly help Annakin save Padmé? How can they help the Senate and the Galaxy from falling apart?
You can see why Annakin might become disillusioned with them. The script should have put Annakin in an "impossible choice" situation. Perhaps a situation where he had to choose between saving his wife and catching Palpatine (although of course the script couldn't have allowed her to really die: just to think she had died, since she had to have her twins in secret still). A situation where Obi-Wan and the other Jedi were telling him to Let Go of his attachment and focus on the bigger picture. I mean, this isn't rocket-science! If the scriptwriters could have had Lex Luthor and the Green Goblin put Superman and Spider Man in precisely this dilemma, why couldn't Lucas have thought of it? All it needed was to prevent the loophole that Superman and Spiderman always get: of being able to save the world and the one they love. Just such a tragic choice, coupled with the detached and potentially rather barren philosophy of the Jedi, would have done the trick nicely.

Note also that Luke really isn't your typical Jedi. He's more like his father in that he's passionate and clearly ready to fall in love at the drop of a hat. Of course it was too late to fix the dreadful mess which was Return of the Jedi, but if Lucas had really thought this through from the beginning, he could have had Luke be the one who finally brings balance. It's rather sad that he hasn't done more with the 30 years he's had than to "perfect digital eyelash rendering".