Some weeks ago, Mrs. Impala and I went to see the latest Spiderman movie. Afterwards, I asked her if she wanted to go home and watch the (then) latest episode of Heroes, and she replied "No, I don't think I could deal with watching Peter Parker playing somebody who isn't Peter Parker immediately after watching Peter Parker being played by somebody who isn't Peter Parker."
I don't think Tobey Maguire is a terrible Peter Parker, but he just isn't quite right. Milo Ventimiglia, on the other hand, was born to play Peter Parker. Let's hope that if there is a Spidey 4, Maguire is indisposed and the producers have the sense to turn to Ventimiglia.