The Denver Broncos are the only team out of the eight original American Football League franchises to have never played in that circuit’s championship game. Indeed, they never finished above .500. Their woes continued past the 1970 merger with the National Football League, but in the late ‘70s, their fortunes finally turned around. Since their first Super Bowl appearance following the 1977 season, they have been one of the most successful teams in the N.F.L., booth on the field....