I'm all for going with a new director and cast. I thought Routh was okay, but he was a bit too slender. Tom Welling from Smallville has the right type of build for the role. He's muscular, broad chest, but not like he's on steroids. As for Routh's performance I blame Singer. I think Routh could've done a good job if Singer hadn't had him trying to act like a wan Christopher Reeve.
Bosworth was just a terrible choice.
As for Luthor in a new film. I think Lex is a credible villian, Clancy Brown and Michael Rosenbaum have proven that. It's a matter of approach. Spacey was brilliant casting, but once again I think it was misdirection which hurt his character.
That being said, I'm not opposed to seeing other villians, with Luthor playing a supporting role or no role at all. It is time to see Brainiac, Darkseid, Doomsday, Parasite, Metallo, Bizarro, etc. I think the FX today could really make them pretty awesome villians. As for Zod, I'm not sure they should go there again-Terrence Stamp just gave a great performance. I would rather see Jax-Ur and Mala from STAS as the Kryptonian villians. It would be new character territory for the writers/director to explore.