I definately think Tom Welling should step up into the Superman role. He's still rough around the edges as far as acting goes, but he does fit the Superman role extremely well and it'd be a HUGE pleasure to see him on the big screen.

And as far as being darker... well, you guys obviously haven't watch Smallville then if you don't think Superman can be 'dark'. Obviously it isn't going to be Dark Knight quality, because let's face it- the Joker and Twoface nomnom that market. But it definately can take a darker tone instead of being all fluff and stuff.