Fix up the dialogue for one, so the love story'll be a bit less cliche (though, I've only written for horror, admittedly writing romance would be an experiment for me)
Maybe change the whole trilogy around so Episode 1 will be the start of the Clone Wars, and have Anakin and Padme be more like Han and Leia (Rather then JUST being in-love and trying to hide it, give it the opposites attract treatment)
Episode 2 can show more of the Clone Wars and end with Anakin turning to the dark side, while episode 3 can have the Jedi purge, Anakin going into the suit, and Luke and Leia's birth.
Personally, I think Lucas is just a poor director, and if he had let someone else direct the prequels, with the same cast and crew, but allow them a couple rewrites to patch up the dialogue, they would have been just fine.