I don't know if the problem is the comparison or the question. I think a better comparison would be Pele. You'd have an opportunity to compare total points differential from the greatest (Gretzky and Pele) to their number twos with similar numbers. You could compare international competition. Impact as ambassadors of the game internationally,etc..
Chamberlain is a superstar in his sport, no doubt. But Gretzky has what? 60 records? Could lead the NHL in all-time points just on his assists totals? The true test of defining Gretzky's dominance in his sport is that many examine incidental minutiae as justification why his all-time leading goal totals don't stand under scrutiny. Too slow, too small, over-protected...We can say his goals totals also stand because one player was sick in his career or another too often injured or another didn't have the team around him or whatever else that seems to fit the sub-hobby of diminishing the goals record. But the truth is, we are criticizing a player we likely still don't fully understand and maybe isn't fully understood by his peers.
In order to compare who dominated, we need to examine the distance between first and second in each categorical instance. Take total points scored by the forwards as an initial, primary instance.
NBA:
1) Kareem Abdul Jabar - 38,387
2) Karl Malone - 36,928
------------------------------------
5)Wilt Chamberlain - 31,419
NHL:
1) Wayne Gretzky - 2,857
2) Mark Messier - 1,887
It seems strange that in order to fairly compare Gretzky and Chamberlain we would have to exclude from consideration what best defines asymmetry and thus dominance within fair competition.
When even the arena they are being compared in must be retrofitted just so the other can compete, shouldn't that be yet another reason to comfortably conclude that Gretzky is far and away the more dominant of the two?
Many of Gretzky's records are a product of his era however. He was the best player by a good margin in the highest scoring era of his sport.
Wilt on the other hand was the most dominant of his era by a healthy margins that does not skew over the 50 years of the league from when he came in to present day. Like I touched upon his minutes per game. Only 5 players in the history of the NBA averaged above 40, several in this thread have implied there were a hell of a lot more.
Here's the Top 10:
1. Wilt: 45.8
2. Russell: 42.3
3. Robertson: 42.2
4. Iverson: 41.1
5. Baylor: 40
6. James: 39.3
7. West: 39.2
8. Lucas: 38.8
9. Pettit: 38.7
10. Sprewell: 38.6
Orange=predominantly 21st Century
Blue=predominantly 90s
Purple==predominantly 50s
Green=predominantly 60s
While 6 out of those 10 were in the same time period, extending down to the next 10 you get more representation of the 50s, 70s, 80s and 90s with current star Kevin Durant sitting at 16th.
Now if you go and look at the Top 20 list of NHL PPG career leaders you get 3 active players in Crosby/Ovechkin/Malkin who will drop down as they continue to play out the second half of their careers and Jaromir Jagr who was the highest scorer of the DPE at 17, and he had some nice seasons in the early 90s to help him out playing with Mario.
Discounting Crosby who sits at #5 currently, out of the Top 10 only Bobby Orr, Forsberg and Esposito did not play multiple seasons in the 80s with Forsberg having a shortened career and a testament to Orr's greatness. Meanwhile the NBA PPG leaders Top 20:
4 active players (1 is nearing retirement at 10th and James is 3rd having less seasons remaining than played)
7 additional players who started NBA after Wilt retired
3 additional players who came in Wilt's later years
Any way you dice it, Chamberlain transcends eras in a way Gretzky never will. Wilt was the best blocker, scorer, rebounder and only non-guard to lead the league in assists.
His playoff resume lacks because of the dynasty he could not beat on his own. End of story. He could have joined the Celtics and won 12 titles. He instead chose to dominate and the force of his team and dominate he did.
I think people here get lost in careers and forget the title is DOMINANCE. Both physically and by production, Wilt is head and shoulders above Gretzky.+