When discussing on general football forums, most fans of other teams seem to mean that RvP is the best striker in the world aside of Messi, and many of them also say that he has been the third best player in the world this year. I agree with them, and I think more people here would have too, if he had signed a new contract.
Career-wise, of course Zlatan is better, because RvP has never been injury free for long, but at the moment (the last year), I will say that noone else than Ronaldo and Messi has been better than van Persie.