His performance isn't good but neither are most of the performances in the film, even by talented, well-established actors. The writing and direction is really to blame here. It's hard to be a good actor when you're delivering terrible lines in front of a green screen, talking to a tennis ball on a stick.
As a side note they really should have aged up Anakin to around 13 or 14 instead of like 9. It would have allowed them to find a more charismatic child actor, and removed the weirdness of the Padme age gap.