Rivalries usually generate between division foes, or at least teams within the same conference that meet frequently. For the Cowboys, two of their biggest rivals outside of their division have been the Packers and 49ers, both of whom they frequently came into contact with in the postseason at various points throughout history. But the fact that the Steelers are also considered a rival speaks to the greatness of these two franchises.
For starters, the Steelers are tied with the Patriots for most Super Bowl wins by a franchise with six, and the Cowboys are just behind with five.