Like Ghostbusters I though Anakin would be a more mature character. Luke's age, but more akin to Han Solo in experience and attitude. Though I would have greatly preferred if his background was simply left in the dark, and that Owen was his real brother from the beginning, I like the idea that he was a slave.
Contrary to many people I expected Anakin's turn to be very evil. Not the Shakespearian drama Lucas so ineptly tried to pull off, not some melodramatic twist, just evil. Anakin should have become Vader knowing into what he would turn into. Lust for power? For knowledge of the Force, becoming the ultimate weapon in the Galaxy (hence his attitude in A New Hope about the Death Star being insignificant compared to the Force). Just in my humble opinion his redemption at the end of Jedi would have been more powerful if it was the redemption of an actually evil and not a tragic man.
In short:
- a better space battle with a story and an impact on the plot of the movie - a set up, beginning, and an end, like Endor. Instead we got a dozen mindless minutes of ILM's CGI prowess.
- Windu finally getting something better to do. I hoped Lucas would pull a reverse of Jedi throne scenes, just sitting there and manipulating Anakin/Vader to destroy Windu. Mace Windu should have been the best Jedi Knight on par with only Obi-Wan, yet Vader in his prime, with the suit, should have crushed him. I think we desperately needed a show of force from him, why is Darth Vader so feared anyway?!
- Obi-Wans vs Anakin handled differently. Preferably at the beginning of the movie (with Anakin's fall being the final of Ep.II), so he can spent most of the time in the costume. Not like people now presume Vader's costume is like an advanced wheelchair that let's him move at all, but rather the suit should have made him even better at annihilating Jedi.
- I didn't like the concept of the imposing Jedi temple on Coruscant, but if it had to be there, at least we should have seen the stormtroopers assaulting it and defeating the actual Jedi, not some children.
- Proper ending for the entire Separatists story line. Entirely wasted throughout the prequels, even though it had a lot of potential (a twist, what if they had been the good guys?)...
Generally less scenes that strive so hard to be visually game-like cool for teens that they end up being stupid.