I don't really understand this arguement. Sure it was easier to score in the 80's. We all know that. But it was easier for EVERYONE to score in the 80's. The fact that Gretzky won 10 scoring titles and 9 Harts doesn't somehow lose its meaning just because it was easier to score back then, because he was playing under the same conditions as everyone else. If the Fuhr wore today's goal equipment, and the rest of the league wore the stuff from the 80's, then it would matter. But that's not what happened. Gretzky played in the same environment as his peers, and dominated far more than Crosby has, playing against his peers.
I don't really see how that point is even debatable. Crosby has 1 Art Ross, and 1 Hart, after 5 seasons. Gretzky had 4 Art Rosses, 5 Harts, and had even tied for the Art Ross his first season but lost it on goals. This is not to diminish Crosby's achievements, but to say he's in the same ballpark as Wayne is simply wrong. In the past 5 years that Crosby's been in the NHL, we've had 5 different people win the scoring title. NO ONE has come to clearly dominate their peers in the NHL today. Crosby and AO are elite in the sense that they are always among the best, but they aren't consistantly THE best year after year after year. Gretzky and Lemieux were, and by huge margins.
People can say what they want about conditioning, shorter shifts, etc, but there's no reason people like Gretzky or Lemieux wouldn't have adapted. Both played 30-40 second shifts in the Canada Cup finals, and look how well both played there. Furthermore, we've seen players like Roenick, Chelios, and Bourque all play from through the 80s/90s/2000s and manage to adapt to the changes just fine. Mario played in the 2000's and was still great. Gretzky played in the late 90's and was still top 5 in scoring, even as an older player with an arthritic shoulder and a herniated back.
Look at Jagr, as a great midpoint. Gretzky and Lemieux were both clearly better than Jagr. But after Mario's retirement, Jagr went on to win 5 scoring titles of his own. Jagr only overlapped with Crosby and AO for 2 seasons, his last 2 in the NHL. The 1st he outscored both, putting up 123 pts - a mark neither has yet to equal. His 2nd, he was outscored by Crosby, but still outscored AO. Now granted, both these players were young, and 2 seasons is a small sample size. But Jagr was also older, and clearly past his prime. Yet he outscored AO both years, and Crosby 1 of 2. He put up more points during the modern game, against these players, than either have in their careers. And despite all this, no one on earth including Jagr's mom thinks he was better than Gretzky or Lemieux. If today's superstars couldn't dominate an over the hill Jagr, how would they possibly dominate a prime Gretzky or Lemieux?
The "younger players are better" theory sounds great on paper. It fits what many want to think about the sport - that its somehow evolved to new heights never seen before, or the mentality that what's happening now is automatically "better" than what's happened in the past. But this theory falls apart in the face of the actual evidence of players who've played through three decades of hockey and can still compete, or dominance vs the players who overlapped their careers.