Agreed. The biggest/bestest/mostest is pretty obvious since it's such a slam dunk. But the second, third, etc. isn't so clear. Whichever maker is number two is a distant second, and probably not all that far from number three, and so on.
Arguments can be made for Kingman (first Spyders hit the streets in '95 or so) and Brass Eagle (especially the owned-by-Daisy era which saw 'em get into big-box stores even ahead of Kingman) being numbers two and three, though in which order would be pure conjecture without reliable sales figures.
None, however, of the "top" makers- WGP, WDP, SP, AGD, etc.- come close. Yeah, AGD had a five or six year head start on Kingman, and by some estimates sold somewhere around a quarter of a million 'Mags of various styles, but it wouldn't surprise me if Kingman made that many or more just in the last five or six years since Tom stepped down from AGD.