Good post.
I guess it comes down to just what does anyone think the HOF should consist of, is the absolute best, head and shoulders above all the rest, or is it just any player who has great stats, great longevity, championships, impacted the game measurably? You mentioned Terrell Davis, yes he had limited rushing attempts, but Gale Sayers had only 938 rushing attempts, these days that's barely 4 years' worth, Emmitt had more than that in his first 3 years. But if you let Sayers in, who was great but often injured, then you pretty much can't keep Davis out, either.
There are the obvious players like Staubach, Emmitt, Lilly, etc. They were no-brainers. Guys like Hayes you have to dig a bit deeper to find their HOF credentials.
The more you add the Bettis type player, to me it diminishes the aura of being in the HOF. If it was up to me it'd be a more exclusive club.
All Dallas Cowboys. (Just kidding)...