I like Malkin and I actually think he is more talented than either Ovechkin or Crosby.
Unfortunately, Malkin just cannot stay healthy, he has 4 top10 finishes in points in 12 seasons he spent in the league. That's less than what Nick Backstrom has, to give it some perspective.
I am looking forward to McDavid surpassing Malkin's peak (11/12), which McDavid has not done yet, but I think he is capable of doing it. Basically, given what McDavid has already done, the year he does that, he is ahead of Malkin in terms of career.
If that never happens (which would be a shame), I'd say 2-3 seasons like 17/18 plus reasonable longevity will put McDavid ahead.