For me it's pretty obvious that Lewandowski is the only one who deserve this award. It was his best season and he won everything with Bayern while being top scorer in all three competions, not many did this before if any.
I think that because Messi and Cristiano played seasons below average, this would be the year with the greatest chances for Neymar, but with the defeat in the championship final, I think he would not be elected the best in the world.