Out of the three podium finishers I would have to go with Rosberg. Yes, Alonso won it, but I think that he won due to his own team's incompetence (in Quali 2 & when Piquet hit wall). I think Hamilton was the big beneficiary of the race and was on the podium by merit. (i.e. he won the race of the people on his strategy!) However, Rosberg gets the award because he overcame the fact that his Williams is not a great car and a stop-go penalty to come second behind Alonso in the fastest Renault of the season.
Yes, Fisi being in third helped Rosberg when he led after SC1, but he was still able to blast away from Jarno Trulli, who had a bad weekend but was pretty light when Rosberg was pulling away. He also kept Hamilton behind him when Hamilton was actually bothered!