What imo separated the good teams from the great teams IS the ability to win the close ones.
the teams that can get that stop on D to win the game, the team that can with sub 2 minutes left..get down the field and score those points necessary for the win, be it a FG or a TD ...most of the time.
sometimes the great teams play OTHER great teams... then its...can your Defense, stop MY offense and vice versa at the end.
take this past superbowl, two great teams. BOTH defenses could not "regularly" stop the other teams offense, however, at the end of the day, one team had to win, and that was the team that made The Key Play to win the game. stupid call by seattle? maybe, maybe not-overall MOST of the time-(like 99%) that play is a TD or an incomplete pass..this time, the defender- butler- recognized the play from film, Brown, recognized the play from film- locked the front receiver in a block- allowing butler to sprint to position and make the play to win. it was glorious.