The few posters above completely ignoring the value of adjusted stats is exactly what's wrong with this forum. Nobody is saying that hockeyreferences adjusted stats are perfect, but they provide VITAL context to a scenario where it is a fact that it was much easier to score in Gretzky/Lemieux's days than it is now.
3 Points I'm going to make, and I'd like 3 honest answers.
1) For example, taking goals at face value and ignoring the scoring environment as a whole, look at the 1984-1985 season where Mike Gartner was 9th place in goals with 50. Ovechkin has around 5 Rocket Richards where he scored around ~50 goals. Would these outstanding Ovechkin seasons really equate to only being hardly top-10 back in the day?
2) In 1980, $1,000,000 CAD would be worth about $3,000,000 today. Why? Because everything today costs on average, much much more than it did back then. Similar to how everyone scored more goals in 1980 than they do today. So tell me, is $1,100,000 today worth more than $1,000,000 30 years ago, just because it's a bigger number?
3) Let's say all of a sudden the league makes a rule change that forces NHL goalies to wear equipment that they wore 35 years ago, and this therefore increases scoring to 50% higher than 1980 levels. If McDavid scores 240 points, does he then get deemed to have 'peaked' higher than Gretzky did, all because of the absolute numbers?
If you answered 'yes' to any of these 3 questions, you are completely ignorant and foolish. As I said, it's hard to find a perfect way to measure between vastly different scoring environments, but to ignore them completely and just say that X > Y or X/gp > Y/gp is just a terrible, closed minded way of thinking.