Superman/Clark Kent: Paul Telfer. He has the size, the height (at 6'2" he is tall enough) He can act from what I have watched. Plus he is the right age at under 30 and is enough of an unknown not to take attention away from the film.
Lois Lane: Olivia Wilde. I am with most people on this one she has the look and the spunk to be a feisty report like Lois.
Lex Luthor: Billy Zane. Hands down this man was born to play Lex Luthor. He has that wicked smile you can tell he has the acting ability to be charming when need be then evil in a blink of an eye.
Mercy Graves: Kristiana Loken. She is perfect. She has been in enough action films such as Bloodrayne and Terminator 3 where she can throw some people around as Lex's bodyguard.
Perry White: Bruce Boxleitner. The man has a resume that includes Tron, Babylon 5, and Tron Legacy. He could easily pull of the Daily Planet editor and chief.
Jimmy Olsen: Michael Welch. He can be seen in the twilight films as the akward high school student, he would make the perfect Jimmy Olsen.
Brainiac: Matthew Goode. Look at him as in the Watchman he can play evil genius plus he can throw down if need be as seen in his fight scenes in Watchman as well. I think he would make a good Brainiac they would just have to do something to his voice to make sound more electronic and scary.
General Zod: Guy Pearce. He can play the villain just see him in the Count of Monte Cristo. He knows how Nolan works and I think he would make a great Zod
Faora: Carrie Ann Moss. Looks the part is familiar with Nolan from Memento and I think she would be great as Zod's lover and right hand (wo)man.
Quex-Ul: Tyler Mane. He has the size and presence to play Zod's Muscle.
Metallo: Andy Whiefield. He can be seen in the Spartacus mini series. He has the look and the acting chops to play the role and as seen in Spartacus he can throw down in the fight scenes with Superman.
Pa Kent: Bruce Greenwood. Seen in the Star Trek reboot he would perfect as Supes dad.
Ma Kent: Linda Hamilton. She can be a B.A. as seen in Terminator 2 but, she also has the ability to play the loving mother I think she would make a great Ma Kent.