Well my first choice would be Tom Welling. He does a good job as CK, but I hate the guy for not wanting to done the suit! Still, the most logical choice!
For a total reboot, then I'd go for Henry Cavill
However, even if inferior to Reeve, Brandon Routh was a fine Supes and I could see them choose him again.
But DC being dumb as they are, I picture the next Superman being played by Hugh Laurie (the guy is in!), wearing a leather suit (that's DAAAARK!), directed by a Nolan (everyone knows Warner thinks this guys died on the cross) and in the ruins of Metropolis (you gotta have a depressing setting, makes more money!)