It really is difficult to compare players from one era to another. The game continues to evolve including goalie equipment, stick technology, the rules, etc. So how do you compare Wayne Gretzky to the NHL's other prolific scorers?
Well the approach I took was to look at the scoring leader over the last 50 years and determine how much more dominant he was than the rest of the league by calculating the margin between the leader and the runner up to the scoring leader. So for instance in 1986-87, Gretzky had 183 points which was 69.4% more points than the next best player behind him. In fact that happened to have been Jari Kurri who likely wouldn't have scored 108 points that season had he not been on the wing with Gretzky.
Below are the top 20 scoring leaders based on percentage lead. Not surprising Gretzky takes 8 of the 9 top spots. He consistently won the scoring championship by a 40% or 50% margin when in most seasons the leader squeaks in by about 5%. By New Years, Gretzky could have taken the rest of the season off and still won the scoring championship.