This poll is the perfect example people vote based on hype and not performance.
The question is who will become the best player. Your ranking list is a perfect example of voting based on the infamous "what have you done for me lately" HF gospel.
But I do believe that those three will develop into better players than Granlund. I was never really high on him to begin with and I don't think he will ever fully overcome the lack of size and strenght he is currently struggling with and become a prominent player in the NHL (as I see the other 3 becoming).
I don't see how anybody could have a strong opinion for or against any of them. 5 years from now, they could all form an elite little cadre of some of the best young players in the game, and it still might not be possible to pick between them. As a Habs fan, I'm happy with Galchenyuk and wouldn't trade him for any of them... but I would not expect any fan of those players' teams to trade their guy for any of the others either. They're all in a close grouping and I don't see how anybody can make a real case for predicting which will be the best.