The truth is at that their very best, all these players were absolutely fantastic, and quite close. So for peak "level of play", personal preference, and no answer is completely wrong.
If you were guaranteed to get the player at their very best for a ~10 game stretch, there's very little separation.
I voted Jagr. His peak lasted the longest, and he put together the most full peak-worthy seasons, which I think is important. Ovechkin is #2, with his 3 year stretch.
Malkin was intermittent, Lindros even moreso due to injuries, and Forsberg worst of all (doesn't even have a perfect storm of a season, 2003 was fine, but weakest "best" season among these players).