Soooo as long as we're resurrecting this ol' thing, here's my more serious answer.
I have no idea who'd be well cast, but I think the look would have to be less pretty-boy and more capable of looking grizzled. To me, the actor wasn't the real problem. Rather, it was the story as a whole.
The way I'd restructure things is to have a trilogy (not a single prequel film), but have it be entirely about the Clone Wars and their immediate aftermath. Maybe make the first film and a half be about nothing but the Clone Wars with Anakin being discovered as an ADULT hotshot pilot who joins the Jedi order (in this version, "padawans" aren't required to be 5-year-olds). The large-scale destruction of the war and the dithering of the Galactic Senate would ultimately lead Anakin to decide that the only way to save the galaxy from itself would be to impose strong, imperial rule, using ruthless control and even brutality to achieve peace. Basically, peace by ANY. MEANS. NECESSARY.
Other things that I might play with...
- The clones are the antagonists, not the Republic's troopers. They're a labor force that rose up a la the various Servile Wars in the old Roman Republic.
- The clones would be a mixed bag. You'd sympathize with them, but they'd also be fighting with as much brutality as possible to force the Republic to come to terms. They'd have basically been little more than slaves, and would use any means available to fight back.
- The Republic would ultimately decide that all clones must be exterminated and cloning itself would be absolutely outlawed. Droids would be seen as a better option because they'd be more controllable due to programming. Not everyone would believe this, though, which would explain some of the anti-droid sentiment, as well as some of the more restrictive attitudes towards droids that we see in the Star Wars films.
- The Jedi would start out supporting the Republic, but would eventually reject the decision of total extermination, believing it to be antithetical to the light side of the Force. It would be this decision that would result in them being labeled outlaws and traitors. The process of their extermination would be underway by the middle of the 2nd film as the war wraps up and the Empire takes control. The third film would showcase the rise of the Rebellion.
- The Emperor would be a talented politician who would take advantage of the situation and enhance his abilities through his mastery of the Dark Forces of the Sith. He would ultimately turn Anakin to his cause. Anakin would see in the Emperor a path to permanent peace, and so would sign on with him. The Emperor would simply want total power for its own sake but would be happy to use Anakin as long as he could.
- Re: Anakin's wife, she'd be with him by the 2nd film after the war, but would escape while pregnant for fear that her child (it's unknown she's having twins) grow up in an environment where Jedi were hunted. Her death in childbirth would be faked, and she'd move to Alderaan where she'd work in the Organa household until Leia was appx. 2-3 years old, at which point she'd die and Bail Organa would adopt Leia as an otherwise unnamed "war orphan" who would be raised as an emissary of peace. This would be a political act of the ruling house of Alderaan, but would explain why Leia remembers "her real mother."
- Luke's "uncle" would have actually been one of Anakin's friends growing up. Anakin left Tatooine to join the war and never came back. Owen always thought this was stupid, since the war didn't have anything to do with a planet like Tatooine where nobody was wealthy enough to use clones except the Hutt crime bosses and their associates.
Basically, Anakin's motivation would be to prevent the kind of war that happened with the Clone Wars from ever happening again. He'd hate the dickering of the Senate and the slowness of representative politics. He'd recognize that he's doing villainous things, but believe he's doing them for an ultimately good purpose, and become a very "end justifies the means" kind of warrior. He'd still be conflicted about this, though, and hate himself for doing it. Ultimately, that'd be what Luke senses in the OT and uses to turn him back from the Dark Side. Anakin would view himself as a monster, but believe that it's necessary for him to be one to save the galaxy. Luke would show him that he's wrong.
There'd be no Jar Jar, no midichlorians, no prophecies about chosen whosits, no "roger roger what's our vector, Victor?" droids, etc.