Its only icing that Tobey "looks like Peter/ Spiderman." His acting ability saves the charactor. It would be easy to overplay Peter's social awkwardness and his moony gawking at MJ. This would turn our stomachs faster than the taste of Spidey's webbing. You may say that Tobey isn't acting- but that's better than overacting. His performance is understated- and without that this role would quickly become a charactiture of a sensitive, love-lorn geek. Reveiw his lines, and think about the many scenes where he's required to stare sensitively at MJ. With all that repitition, I'm glad he didn't hit us over the head with it. Also, he's hiding himself, suppressing himself. How else do you portray that except by being a little wooden? And Peter is a polite, reserved, private person- until he is Spiderman. And I think that was nailed also- with the Woo-hoo's and the mugging for his own cameras.
In thses movies, it seems that MJ is the star. So you need an actor that has chemistry with Dunst. I think he does. Then again, that may be more about her than it is about him.