Put it this way, Gretzky had three years where his assists would have led the entire NHL in points and one other year where it would have been tied (although that was Kurri who had the 135 points that year). Even if you ignore the raw totals let's just try and find a time when anyone came close to this mark - once.
Orr had 87 assists in 1970 when the next best player (Phil Esposito) had 99 points. He won the Art Ross just one other time in 1975 and wasn't even close. Esposito or Lafleur weren't close in either of their Art Ross years. Bobby Hull only has one year worth mentioning and its 1966. It is the opposite of Gretzky because Hull had 97 points with 54 goals while second place in the NHL had 78 "points". Still not close. Elmer Lach with 54 assists while Richard had 73 points. Not close either. Surprisingly Howe was never even close himself, not even once. I think Lemieux has a slight chance to do it once had he not been injured in 1993, possibly. Lafontaine was 2nd in PPG at 1.76 while Lemieux had 1.52 assists per game. Still a stretch though.
Post Lemieux we never saw Jagr come close. Thornton had 96 assists in 2006 which is very close to any non-Jagr player that year (Ovechkin was tops at 106). Even arguably the best playmaker over the last few seasons, Henrik Sedin wasn't close to it in 2010.
This is just an incredible feat and utterly mindboggling no matter how many times you look back at it. The scary thing is, Gretzky almost did it again in 1991 (122 assists with 2nd highest point total being Hull at 131). Only then did age, Gary Suter's hit and burnout force him to slow down.
So really, in NHL history we have never seen anyone do it once. Gretzky did it three times and on a couple of them there was some serious seperation from the next highest point getter in comparison to his assists. And we still have debates as to who the best player of all time is...........