(I am just catching up with this thread; hence my response to a comment from several months ago.)
I must say that I really dislike this comment.
Even if we accept that the majority of lower-league players could not play in the NFL or the CFL, the fact remains that those players are still elite athletes. Someone who is 80% of NFL quality is nevertheless performing at an extraordinarily high level; and we see any number of individual performances in the AAF and all the indoor leagues that demonstrate this fact. These players should not be regarded as "rejects", or equivalent to a guy who was cut from his high school team.
Furthermore, there are only so many jobs in the NFL and CFL; and only a tiny percentage of all the football players who are talented enough to play in those leagues ever get the opportunity. Notwithstanding all the scientific pretense involved in using metrics at scouting combines, scouting is in fact very dependent upon the dominant conventions (a polite way of saying "prejudices"). And even the metrics themselves become a kind of mythology; a slavish reliance on sprint times and bench presses tells us nothing about the many intangible qualities that make up a competitor. For every NFL or CFL player, there are dozens to hundreds of other players (depending on the position) who could do the job equally well. These guys wind up playing in the AAF and other lower leagues.
The AAF has been successful in presenting high-level competition in a way that is interesting for spectators. The relatively good television ratings are very encouraging, and indicate that plenty of people see these players not as rejects, but, rather, as the quality professionals they are. The XFL will also be drawing players from the enormous pool of high-quality players who do not have NFL or CFL jobs. If that league fails to match the AAF's modest success, this will be for reasons other than the level of talent available.