I think Ronaldo has performed better than Messi for the most of this season. Last year the complaint was that he had failed to perform in big games and in every el clasico (except the cup final) messi outshone Ronaldo. But this year Ronaldo has led the team to La liga title and has also overcome the pressure that he has in big matches. Even in the clasicos, Ronaldo has scored in most of them whereas messi even though brilliant has not performed well enough.
Considering that Cristiano and Messi are going to be frontrunners for the award this season also (they are miles ahead of everyone else. Even van Persie and Mario Gomez are far, far behind.), I think Ronaldo has a much better chance of winning the coveted trophy in 2013. But everything now depends on the last few liga matches left. If Ronaldo manages to overtake Messi's goal tally of 63 by some miracle, it would make him the clear favorite.
Also I think next year Real Madrid will have more players in World XI than Barca and Munich and almost certainly more than Chelsea because they lost the semi-final on penalties which doesn't show an player's talent.
My World XI:(4-2-3-1)
Defenders: Danny Alves, Pepe, Sergio Ramos, Fabio Coentrao (I really think he deserves it)
Defensive Midfielders: Xavi Hernandez, Xabi Alonso
Striker: Karim Benzema (could have been van Persie but I don't think he can create as many chances or even score with a volley from the far post)