I would personally name Lidstrom as the best dman to ever play not named Bobby Orr. He was the Roger Federer of defensemen. Incredible to watch. My Orr-less Mt. Rushmore is Lidstrom, Niedermayer, Bourque, and probably controversial, but Pronger, I absolutely love the way he played. If he continues on as he is, Karlsson will be added to these 4, he's Orr 2.0.
And on the Crosby-top 5 debate....to me, if he's not already 5th, he's 6th. We can't compare stats between players face up, we have to take into consideration just how God damned hard it is to score today, and realise that Sid is STILL 5th all time. Teams aren't relying on 2 or 3 guys to score, they now have 4 lines that are expected to contribute, thus spreading the points around even further. Goalies and coaches are SO GOOD. There is a salary cap designed to make as many teams competitive as possible and the Pens have still won 3 cups in 8 years, and are set up to compete for probably 4 or 5 years more yet. He lost 2 years in the very prime of his career, And to me he is playing the best hockey of his career the last two years.
When all is said and done, it's going to be the holy trifecta of Gretzky, Bobby, and Sid sitting atop the pantheon of hockey.