I think he's top 10 for sure. I'm not sure that he's the best defenseman in the league, even as the reigning Norris winner. Not sure he's top 5, but I don't think it's crazy either.
There really are no perfect defesemen in this generation. Maybe that's because the game is beginning to lean back toward speed and offense, but you see the warts on pretty much everybody from time to time, these days, in a way that didn't really happen in Chara, Pronger, and Lidstrom's primes. ...Well, in Lidstrom's case, he'd probably be the perfect defenseman in any era.
But anyway. We're lucky to have him.