Margot Kidder can't act. Gene Hackman can act, but didn't in the Superman movies. He hated being Lex Luthor, it was just a paycheck to him. The 3 TV Luthors we had since did much better jobs. And I'm sure Kevin Spacey (who is a fan) will actually put some of his acting skills into the role.
I will agree that Reeve did a good job in the movies, he was the only one to turn in a good performance.