I think Zlatan's behavioral (not quite sure if that's a real word) are a bit overhyped...
He's been at Juve for a season now, and he hasn't gotten into any trouble to my knowledge. I also can't see how you can fault him for moving to Juve, because he wanted to play at a bigger club and on a bigger stage such as Serie A. Does that really make him any less loyal than your average professional footballer?
Look at Davids, he was a great player for us, but when it came to renewing his contract, he left without a second thought because we didn't want to meet his wage demands. That doesn't negate his years of good service as a world class player, but it shows that his loyalty to us was only attached to how much he earned at the club.
As for the original statement, no i don't think he's the best in the world. Far from it, but if he improves on his weaknesses, focuses on the tasks at hand and plays more for the team, i think he could have a good shot being that one day.