Sorry if I came off as snipey, Bob: your post was quite reasonable.
Not that far... not that close. Gretzky put up 706 goals in about 11.5 seasons (up to his 30th birthday in late January, 1991). Bossy racked up 573 in ten seasons. I'm of the firm opinion that with (a) the Islanders' contemporary decline, and (b) Bossy's turning 30 during 1986-87, he wasn't going to keep up his pace beyond that point in time. Anyway, Bossy would have needed 706 - 573 = 133 more goals in 1.5 seasons to match Gretzky's 12-season pace. Was Bossy going to score 67 goals per season, either out of the QMJHL at age 18, or past age-30 on a declining Islander team?
I'd definitely put Bossy solidly in the tier-2 of all-time goal scorers (the more so in consideration of his 1981, 1982, and 1983 playoff runs), but he's behind the 'big 5' I listed above.
I can't really see how Lemieux was more consistent at scoring goals than Gretzky. I think we can safely say that Lemieux was better at scoring goals after each's first 9 or 10 seasons in the NHL... albeit Lemieux had only a couple of partial seasons after that.
Anyway, for goal scoring, I think I'd rank 'em something like:
Tier 1:
Rocket
Hull (senior)
Wayne
Mario
Ovie
Tier 2:
Gordie
Espo
Bossy
Hull (junior)
Tier 3:
A bunch of guys, including Lafleur, Bure, Dionne, etc.
(not counting players from the 1920s' era, mind.)