I thought that the film was passable as a form of killing a few hours, but overall a bit contrived. It allowed no characterization of Superman or of the other characters; there was no insight into Parker or Superman's emotions or reasoning behind any of it.
Spacey as Lex Luthor was indeed a good combination, and I think the strong point of the film, but fell victim to the pitfall of "great actor+sub-par role= ridiculous." He delivered some power, in particular with his dialogue, but we were left in the cold when it came to his motivations to destroy Superman on a personal level, rather than just wanting him gone for the crystals.
the film was passable as entertainment, but I wouldnt say that I would ever consider watching it again.