Superman/ Clark: Christopher Reeve. I'm of that age. No-one will ever top him for me, though I thought Routh was a superb recast. If they make another movie soon, I'd like to see Routh back or else Jon Hamm.
Lois Lane: I think Charisma Carpenter circa Seasons 1 - 3 of Angel would have been ideal. Ditto Courtney Cox around the first few seasons of Friends.
Lex Luthor - Daniel Benzali, best known as Teddy Hoffman from Murder One. I always liked Lex drawn as a chunky bloke and Benzali's husky voice is appropriately villainous.
Jimmy Olsen - Ron Howard circa Happy Days
Perry White - Jason Robards circa All the President's Men. A little typecasting perhaps, but still ...
Pa Kent - Dennis Quaid
Ma Kent - Though Smallville has gotten dire lately, I actually like Annette O'Toole a lot in this role
Jor-El - Brando works for me but I think Julie Christie would be a better Lara than Susannah York, the actress from the first two movies. I've stolen someone's Ma Kent, sorry about that!
General Zod - No-one could bellow 'Kneel before Zod!' like Terence Stamp
Lana Lang - Laura Prepon from That 70s Show