Crosby and McDavid play two different games. McDavid is all speed and flash, Crosby is more gritty and cerebral.
In the debate about who's better at their peaks, the McDavid fans tend to look purely at the skill (to which there is little argument on who's better) but look too little on Crosby's superior IQ and strength on the puck.
The fact of the matter is that for all Mcdavid's flash, he should be winning the Art Ross every year by at least 20 or 30pts. But... MacKinnon and Kucherov are always right there with him. Those two are very highly skilled in their own rights, but aren't at McDavid level. However, they make up for it with grit (esp MacKinnon) and IQ (esp Kucherov).
And remember that 99 guy with 2857 career points never stood out skill wise. He just thought the game at a level his competition could not.