Film after film, I am convinced that Kevin Spacey is actually not a great actor. Parker Posey though <3 I kinda dug her part but I have a sort of thing for her.
But the whole Superman returning to earth thing. . .I understand it was a plot conceit, but they never even really explain why he left in the first place. Fuck, we're not even sure when he left. Some of the events of the second movie apparently happened, but not all of them. So without knowing WHEN he left, it's impossible to understand WHY he left, and thus his whole "returning" just feels like a lame, unexplained plot device.
And the Supie Stalker bit is absolutely embarassing. Fuck, the whole Emo Superman thing is just so wrong that I doubt the writers really had much experience with the comics or previous movies.
And the return to Smallville is totally pointless. Yes, we get a little emotional moment with Supes and his mom, but it did absolutely nothing to serve the movie's plot. When a movie is as long as SR, fat needs to be trimmed, and that Smallville sequence was totally, totally fat.
EDIT: Yeah, the airplane sequence is cool. The only good part of the movie, really.