A couple points. There is a method for adjusting pure stats by comparing overall #'s of assists and goals/game played. Stats, Inc did that a few years ago in their hockey enclyopedia. You take the average number of goals per game and assists per game for every season, then you find the global average, and adjust every players stats based on a comparison between that years average vs the global average. You also need to decide on a standard # of GP, and then adjust for years where the schedule was different (eg, if you choose 80 games as a standard, and a player played 30 out of a 40 game season, you multiply by 2). This is a HUGE job however, and unfortunately there just isn't a comprehensive DB out there you can Download to run these kinds of heavy numbers.
this method is a decent compromise, HOWEVER, I must bring up a point that was mentioned in the Greatest Scorers thread. Finishing 7th in a 30 team league is a MUCH bigger accomplishment than finishing 7th in a 6 team league. There needs to be an accomadation for the bigger pool of teams and players.
I suggest the following if you want to do a "Round 2" of this kind of analysis.
Take the number of teams in the league as your cutoff. So in a 21 team league, you would count points for the 21 top snipers/playmakers/scorers. 7 points still go to the leader, 1 point to the last place player. The interval between the positions would be 7/#of teams. In this case 7/21 = .3. So 1st place would be 7, 2nd 6.7, 3rd 6.4, etc... Additionally, rather than your bonus points thresholds for dominance, try this: +1 point for every 10% ahead of the next closest player (rounded down).
This, I believe will give you a more representative reflection of snipers, playmakers & scorers through the years and will un-skew the results from the Original 6, and early era (1920's/30's) players.