I don't think they did a good job on the progress of Anakin Skywalker to Darth Vader. In Episode I, Anakin was a cute little kid with an attitude. In Episode II, Anakin was an angry, arrogant teenager. I could see where Darth Vader could come from that. But in Episode III, Darth Vader was actually a pretty nice guy. He cared about Padme, whereas he looked like a stalker in Episode II. He didn't lose his temper much in III, where he always looked mad in II. He only complained a little bit about not being made a Master in the Jedi Council in II, and that seemed justified. He was even on the verge of arresting Palpatine for being a Sith Lord. Then suddenly, he's kneeling at the feet of Palpatine and killing little children. But he still sheds a tear.
And even that wasn't like Darth Vader in the old movies. Darth Vader in Episodes IV, V, and VI was an arrogant, confident, powerful warrior who was in complete control. He never said he embraced evil or had any kind of philosophy. He was just doing what had to be done. He was on the Dark Side, but he said it was because of the power, not because he wanted to save anyone's life or defend the Empire. Man, I wish we could get a do-over on the new movies. Maybe in 20 years, they'll do a remake of the whole Star Wars series, like they did a remake of The Longest Yard and Bad News Bears.