The only time I can't take discussions comparing players in different eras seriously is when they're judged solely by stats. The only objective way to compare them is by comparing league standards of the time (quality of league talent, salary structures/free agency, goaltending styles, health regiments, etc.) as well as personal physical attributes that would translate no matter what era the player played in.
I grew up watching Lemieux as closely as one can being a Pens fan and all, and despite the tendency for favoritism can state with absolute confidence that his bread and butter forehand backhand deke that he'd routinely score with was for the most part only as effective as it was because every goalie had to play 10 feet in front of the crease just to have a shot at stopping a slapper from the blue line because the stand-up/kick save style was so inefficient and glaringly inferior to today's quality of goaltending. I could point to a number of goals from his highlight reels that would never be scored in today's game because they were simple slapshots past goalies who were barely covering 50% of the net. But one could also point to his inarguable physical advantages of his frame, reach, and perseverance through adversities that would translate to any era and try to extrapolate from there. That angle I would buy and am of the same opinion when comparing someone like Mario to this era and any future one. His stats speak for themselves even if they're artificially raised compared to now (especially considering he still produced gaudy numbers relatively close to the advent of post-lockout hockey), but his physical attributes would likely have allowed him to dominate in most any era, just not to the same degree.
The people I'll never be able to find common ground with are the people who obsess over stats alone regardless of context. Such as Gretzky's records for example because they're so impossibly gaudy that they're literally unbreakable, ignoring the facts surrounding the absolutely fortuitous circumstances his career just so happened to occur during such as the highest scoring era in league history (to be fair inflated by his own production), playing his prime on dynastic teams when it was easier to keep a team together, and perhaps most importantly of all the inarguable weaknesses of the popular goaltending styles at the time among other factors. No player ever again will have the same advantages Gretzky did that were almost completely out of his control but still benefited greatly from, thus no player will ever realistically be able to prove they're inarguably superior in a direct comparison.
Dan Marino retired the most prolific passer in NFL history, and his records are likely to be bested by numerous QB's over the next few decades almost solely due to rule changes and league trends that benefit offensive production in the modern game. Now this isn't entirely out of the ordinary, at one time the three pointer didn't exist in Basketball, but because of these inconsistencies between era's one has to take into more than just raw stats if you hope to have a worthwhile discussion. The limits to human physical capability are only so high, and each advancement in team building, coaching, training and healthcare that raises the talent floor of the league reduces the ability of any one player regardless of individual talent from being able to stand out from the pack. If the Lebron James of hockey came along, a physical freak even as a teenager, he'd still have to play within the limits of today's ever evolving efficiency of how the game is played, coached, and instructed.
Off topic perhaps from the discussion surrounding Crosby, sorry for the rant.
