If we're talking pure #9s here:
1. Lewandowski has been on an absurd level this year, absolutely bonkers, and has also been ruthlessly consistent for almost a decade. 9 straight seasons of more than 25 goals in all competitions. 5 straight seasons of more than 40. Has hit 30 goals in a 34 game Bundesliga season 3 times in the past 5 years (and hit 29 in one of the others).
After him, there's a cluster that I think can broadly be divided into older guys who are still at an extremely high level (Aguero and Benzema specifically jump to mind here) and younger guys who are rapidly approaching this top tier (Haaland and Werner in particular), with Harry Kane operating in a weird middle space between these two groups.