Natalie Portman is an award winning actor and quite good in other movies. Hayden Christensen might be terrible, but you can't come to that conclusion solely on his performance in episodes 2 and 3 because clearly even a really good actor couldn't act well in that situation. The blame has to fall on Lucas. He thought he was inventing a new form of film-making where he could fix everything in post production so he didn't push for good performances. He was wrong.
Nailed it. You should get a +5, Insightful for that.