While this graphic is awesome, it obviously carries a bias related to what teams a player has played on, and what league they have played in. A forward playing alongside good playmakers will score much more frequently than one without them, at the same time a playmaker with a good forward will get much more assists. Also, the play-style in different leagues can often be different, with more goals scored on average in some leagues than others.
I wonder how one could create a statistic that takes those things into account, by somehow "normalizing" the number of goals/assists a player has based on who they played with and what league they played in.
Also, I think it's really interesting how that graph "curves up". It looks like there's a kind of trend where players getting a few more assists correlates to them scoring a lot more goals, and while almost noone has more than .35 assists per 90, there are quire a few that have more than .4 goals per 90.