I think there is two issues, one that Hayden had no control of, and one that he had total control of.

1. The portrayal of Anakin Skywalker? This one Lucas is responsible for, so I give him a 2.

The whole way Lucas made Anakin Skywalker was all wrong from the start. He should have been totally likeable in Episode II, not some whining little teenager. He should have been the golden boy, the hotshot, the cool guy everyone aspires to be, and Lucas made him the opposite. If he was 'The Golden Boy' from the start, then his fall to the darkside would have been more tragic, cause everyone would have felt for the character. It would have made a great father/son contrast. Luke was awkward, a little dorky in Episode IV, and he turns out to be the one who is the resilent one. Anakin was a hotshot, cool guy, who had it all, and blew it to go to the darkside, as he is the one in the end who was flawed.

2. Acting of Anakin Skywalker? This one Hayden is responsible for, so I give him a 4.

I'm sure Hayden is a nice guy in real life, but he can't act for shit. He is just another pretty face in Hollywood who is there for his looks, not his ability. Every dramatic scene Hayden can't pull off, as it turns out laughable, the death scene with his mom, the fireplace scene with Padme, on Mustafar with Obiwan/Padme, I could go on and on. The only scene he pulls off is when he confesses to Padme about killing the tuskens, that is actually a good scene, ruined by Padme condoning someone going on a mass murdering spree???