It's very hard to isolate a particular skill and rank it -- and of course there's a lot more that goes into volume of goals scored than just the player's ability -- but anyway, I'll try (this is just NHL based, btw, if that wasn't obvious):
1. Mario Lemieux
2. Alex Ovechkin
3. Bobby Hull
4. Maurice Richard
5. Wayne Gretzky
6. Gordie Howe
7. Brett Hull
8. Mike Bossy
9. Phil Esposito
10. Jaromir Jagr / Pavel Bure / Auston Matthews
I feel like Charlie Conacher's and Jari Kurri's periods as elite goal scorers were just a tad too short to make the top 10.
It's still early days on Matthews, but if he can get another 60-ish goal season this year, maybe he kicks aside Jagr and Bure and starts to climb up the list further...