After 1991 Gretzky basically went to one final,no wins. no first place finishes.
Howe, in a league offering one first place per season, was part of a first place team 8 of his first 9 season, then added 1 in 1964-65. In his thirties carried a weak team to 4 SC finals, despite incompetent Red Wing management post 1955.
Okay, then, let's do the math here:
Howe spent 26 seasons in the NHL. For 21 of them, there were six teams, meaning a 17% odds every year of finishing 1st overall. For 3 of them, there were 12 teams, meaning a 8.3% chance of finishing 1st overall (though actually it was higher, since half the teams were expansion teams). For 1 of them, there were 14 teams, meaning a 7% chance of finishing 1st overall. And in his final season there were 21 teams, meaning there was a 4.8% chance of finishing 1st overall.
As you helpfully pointed out, Howe finished in 1st overall 9 times in 26 seasons. His "odds of 1st overall success" therefore were 2.29%.
Meanwhile, Gretzky spent 12 seasons in a 21-team League, meaning a 4.8% chance of finishing 1st overall. He spent 1 season in a 22-team League, meaning a 4.5% chance of 1st overall. 1 season in a 24-team League, meaning a 4.2% chance of 1st overall. 5 seasons in a 26-team League, meaning a 3.8% chance of 1st overall. Finally, 1 season in a 27-team League, meaning a 3.7% chance of finishing 1st overall.
Gretzky's teams finished 1st overall three times (2nd overall three times, and the Kings once had the best goal-differential in the NHL, but we'll ignore those). Therefore, Gretzky's "odds of 1st overall success" were 3.4%, actually better than Howe's when the "real" odds are calculated.
So much for your wonky theory.
That's not to say, of course, that Howe's Wings wouldn't have finished 1st overall in a larger League in 1953 or whatever, but you can't just compare the difficulty of 1st overall in a 6-team League to a 22-team League.
And by the way, why are we talking about finishing 1st overall, which isn't of any importance? How about we compare Stanley Cups, or records, or peer domination, or...?
(Again, I have absolutely no issue with anyone who thinks Howe was greater than Gretzky. At times, I am of that opinion myself. I simply can't accept the use of "alternative facts" to make points.)