Top 3. I really only have Duncan ahead of him, though I consider Noah and Marc Gasol to be interchangeable as 2a/2b Centers in the league. I also think both Gasol/Noah drop down a notch if Dwight were healthy.
As great as Noah's contributions have been with the load he's been carrying, they come as a result of a Bulls team that needs his performances more than anyone else. The Bulls, like the Grizzlies, win and lose with the play of Noah and Gasol respectively. It's very evident in their season splits in winning/losing games.
As odd as this may initially sound, for all the accolades I want to give Noah for putting ASTOUNDING minutes, I have to give even more props for Duncan for remaining stellar with fewer minutes. It's a simple matter of opportunity - fewer minutes generally means fewer opportunities to perform. Add to that point that Duncan and Noah are on completely differently trajectories and it becomes even more remarkable for Duncan. I can only dream that Noah will, at 36 years young, come close to performing similarly to the Big Fundamental's performance today as compared to Duncan's 40+ MPG season in 01/02'.
He's been so well rounded I'd love to say he's the best. I still think Howard has been which is amazing given his injuries. I do think he deserves DPOY. You can tell he put a lot of work on his post defense in the off season. Given his Shot blocking, Rebounding, post defense, perimeter defense, stealing the ball from players trying to post him up I have to think he's going to be the DPOY.