Roger is best player in any surface, including clay. But this is the surface where he can lose, but I don't think Nadal can beat him in RG two years in a row. There's only one man that has potential to beat Federer in RG this year. His name is Marat Safin, but I don't think he will be fit enough to beat Federer already at RG. Coria and Gaudio are really crap right now. Nabaldian always chokes in the final matches of a Grand Slam. Agassi won't play RG. Roddick and Hewitt are jokes in clay. Ferrero, Moya and Kuerten are history. Acasuso can't play great for two weeks in a row and he lacks experience. Gasquet will have the pressure and he's too young. Ljubicic and Davydenko can do something, but I can't see them beating Federer in a Grand Slam final.
So, or we have a big surprise (Ferrer, Robredo, Baghdatis again, Monfils) or Federer will finally win RG.
And of course, Federer will win Dubai again.