How do you compare athletes across different eras, then? It sounds like you want to look at absolute results only. That's fine, but it quickly leads to absurd results. If in 2100 the 100m world record is 9.30, and hundreds of sprinters run under 9.58, they are all better than Bolt? And farther in the future, thousands. It's obvious that saying all of them are better than Bolt doesn't mean anything, because their eras are so far apart. You can't compete over time.
In hockey it's the same thing. Looking at absolute scoring totals, there are many players in the 80s who are better than anyone currently in the league. Peter Stastny scored 122 points in 85-86 season, so he's obviously better than Crosby and Ovechkin. Right?
The 100m sprint is an incredible useless analogy to hockey.
Using a one dimensional pure power sport like sprinting or swimming or powerlifting and saying that today's athletes are way better then 20,30,50,70 years ago is fine. But those are one dimensional feats of strength and power.
Being a hockey player is about being great at thousands of things not perfecting a takeoff and acceleration like in sprinting. You can't just "train" to be good at hockey. How are Gaudeau and Byfuglien even in the same league? Why did it never matter that Luc Robitaille is slow as molasses?
You can't just arbitrarily compare hockey to a sport that is so different. Gretzky and Mario had otherwordly awareness. Near complete motor control over their legs, feet, arms and hands. Why is there no one like Datsyuk ever? Or Bure or Lindros or Neely or Ovechkin or Brett Hull. No one really played like any of those guys did, before or after.
Saying "hockey players are better then ever", might be true if you look at the average player in terms of strength or speed. But all stars are not "average" players.
Gretzky and Mario utterly destroyed the other best players in the league or Internationally. They were magnitudes better then the other top tier HHOFers of their era. Also anyone that thinks they just beat up on bad players is wrong. The other teams would line up their very best players against them to try to shut them down as much as possible. When either of them played Boston... And played 24 minutes in a game... Almost all of that time Bourque is on against them. So it wasn't like they just beat up on terrible 4th liners.
The argument that both would face much better players today doesn't really hold much water to me, because they were both massively above average players. And still far better then the best players. The fact that today's 3rd and 4th lines and bottom D are better then in 80's and 90's doesn't really affect them much. And the bigger, better goalies likely affects them less then one would think. The set up a lot of goals where they found teammates totally open. They both shot with absurd acuracy and made great decisions on when and where to shoot. They weren't just blasting pucks on the net very often.
