The PP/ES points thing is interesting.
I am not sure where I stand on that. On the one hand, all points count equally, so who cares? Mario's teams got a disproportionate number of PP-opportunities and he took advantage, as he should. And no doubt it is Mario himself who drew a disproportionate number of those penalties which benefited his team (witness the famous goal in Quebec -- maybe the greatest NHL goal ever -- where the defender basically jumps on top of Lemieux, mugs him, cuts off his breathing, covers his eyes, cuts his stick in half with a chainsaw, unties his laces... and Mario still scores). So it is all the same, in the end.
On the other hand, as mentioned above, teams cannot control how many PPs they get and when. And usually there are fewer PP-opportunities in the playoffs, when it really counts. Gretzky was scoring, at times, 65 goals and 165 points in a season if he had never taken a PP-shift all year! (He was still the highest-scoring player of the 80s if he'd never been on a single power-play the entire decade). That kind of ES dominance does seem important, and here's why: It means, for example, that Gretzky could push the 1st-year Oilers into a playoff spot (barely) in 1979-80, and he could do the same in 1980-81 (he was +41 on a losing team). It also shows how much Gretzky could make every other player on the ice dangerous, in any situation, not only on power-plays.
So, I dunno. At times in NHL history -- like the 70s/80s/90s -- there were a lot more PPs than today, but they weren't always equally distributed. It's a difficult point by which to compare individual players, and maybe not a hugely significant one, but I do think if I have a choice I'd prefer the guy who I know can tilt the ice at ES more so than on the PP.