Personally I'd love to see John Hamm in the role. Ok he's nearly 40, but so what? Even as a kid I always percieved Superman and Lois as being around my parents age at the time. And now I am nearly 40, I'd like to see Superman around that age. Reeve and Kidder were obviously not close to 40 at the time, but they came across as older and mature, unlike the woeful miscasting of Kate Bosworth. Her and Routh just seemed too young.
I know this is just my fanciful wish, and probably not as marketable as having a younger actor in the role.