After reading this article about Ovechkin joining the elite club of "players who had 6 or more 50-goal seasons", I started wondering if there is any data to back up this folk knowledge that goals are harder to get now than they were when Gretzky and Bossy were playing. So, I grabbed the data from hockey-reference.com and produced this plot.
It shows the fraction of goals scored by the top-scoring player in each season to the average goals per game in the whole league, plotted as a function of the latter. So the y-axis is (average goals-per-game scored by top player) / (average goals/game whole league). Only players with more than 40-goal seasons are shown. As you can see, you can believe the hype, as Ovechkin is on par with Gretzky, Howe and Lemieux at about 0.29 (Ovi .285, Gordie .292, Wayner .287, Mario .284). However, all three are outclassed by Brett Hull and Phil Esposito, who clock in at about 0.31 (Esposito at .3123 slightly edging Hull at .3107)!
The points story is different of course...
here the y axis is (average points-per-game scored by top player) / (average goals/game whole league). As you can see, Gretzky and Lemieux clearly outclass everyone, with Gretzky just doing it more often as he was not injured so much. However, you can also see Jagr, Esposito and Bobby Orr making impressive marks on this plot.
One thing not taken into account here is the amount of time each player spends on the ice per game. I'm not sure that has changed much in the last 30 or 40 years, but really the plots should about goals per minute of ice-time. If I ever find some data for this, I'll correct the plots.