Just looking at their Selke finishes, here they are, this is how the voters thought:
Malkin - 46th (2009)
Crosby - 30th (2010), 15th (2013), 18th (2014)
Neither player has come anywhere near winning it. The Selke votes can be a little bit of a crapshoot after 10th or so. Is it really all that significant that you finished 10th or 20th in Selke voting? It isn't like the Hart. You could still have a fantastic season despite finishing 10th in Hart voting. 10th in Selke voting probably means the odd writer thinks you're good defensively (enough) and gave you a vote here and there.
Here is Gretzky with the Selke:
Gretzky - 24th, 25th, 26th
Mario finished 17th for the Selke in 1997
So really, is there a difference with these stars? They all had what amounts to pretty useless finishes in the Selke voting. People recognized that they COULD be responsible defensively and I think that's where it ends. Crosby is responsible defensively, not great. I think he gets more marks for faceoffs and such.
Messier is a guy who is recognized a lot more than any of these guys as being great defensively:
Selke voting for Messier: 8, 9, 14, 15, 16, 16, 17, 28
There's a player I would say is a lot better two-way player and is recognized as such.
And Messier still didn't even get the same recognition as the likes of Clarke, Trottier, Fedorov, Datsyuk, etc. Trottier finished as high as 2nd. Fedorov won it twice. Datsyuk three times. Clarke had high finishes and won it once yet the award didn't exist for half of his career and missed a few years of Trottier's as well. Guys like that are all over the map when it comes to the Selke, they are among the first players the voters think of, Crosby isn't. It doesn't mean he isn't good defensively, it just means he isn't irresponsible. Either way he still trumps someone like Zetterberg or Datsyuk as a better player. But I don't know if his defense is that much better than just what you expect a normal superstars to be.
Toews and Bergeron you use their defensive play as more of a plus in their favour. It is a bigger part of their game. Kovalchuk and Ovechkin you would actually use it against them. Crosby is neither of those options, he's just what I would call "responsible" defensively. Nothing wrong with that, but not a Selke threat either.