I'm not going to rank them, but discuss some candidates for 10-best, roughly chronologically:
Maurice Richard was most likely the first all-time great goal-scorer. He was skilled, focused, determined.
Bobby Hull was probably even better than Rocket. Hull had great puck skills, slapshot, wrist and snap shots, and was excellent one-on-one, and a great deker, with quickness against the goalie. One of the best ever.
Phil Esposito was hockey's first ever super-scorer, and he was a great goal-scorer. Esposito was a very smart scorer, and he's one of the best examples of a player who grew to become a much better goal-scorer than he previously was. Watch Esposito in the slot....his best skill is the spin moves he makes before shooting. These are difficult for the goalie, especially then, when nobody else is doing it nearly as well. Esposito became a master at the mechanics of scoring.
Mike Bossy looked like the first real professional goal-scorer. Many observers thought he was the best-ever when they first saw him. The focus, the quickness, accuracy, strength. He could score from anywhere...slapshot, wrist and snapshots, dekes, from every distance.
Vladimir Krutov was the best goal-scorer of all the Soviet era players. His combination of powerful skating, physical strength, puck skills, and goal-scoring ability set him apart. He was a great shooter, could score from a distance, and went hard to the net.
Mario Lemieux was simply the best goal-scorer ever, without a doubt. Nobody is very close.
Brett Hull loved to score goals. He could score well from all over the offensive zone. Great at finding space, great shooter.
Cam Neely was a legendary goal-scorer. Very good sense of the net, could score very well in close or from a distance.
The '90s generation was full of great goal-scorers, probably as many (or more) greats than the entire first 100 years of hockey combined. In addition to Hull, Lemieux, and Neely, there was Bure, Mogilny, Selanne, Jagr, Sakic. Bure was probably the best of the latter five, and easily one of the five-best goal-scorers ever.
Over the past 25 years....Kovalchuk, Ovechkin (obviously one of the very best ever), Stamkos, Matthews. Crosby, also, has some excellent goal-scoring skills but is certainly behind some of these other guys.
There's other players currently, like Pastrnak and Kaprizov, and, of course, keep an eye on Bedard.
Gretzky, Crosby, and McDavid each have some great goal-scoring abilities, but none of the three would be among the 10-best ever. Same for Gordie Howe.