Best scenario for what? Ratings? I daresay a Dallas/New England Super Bowl would be the highest rated Super Bowl in history.
Story line? A Rodgers/Brady match up would be compelling...but the young blood of Dallas going up against the NE dynasty would be as good a storyline, if not better. Add to that the storyline of Dakota Prescott attempting to be the first rookie QB to win a Super Bowl and you have the league office's wet dream.
Call me a homer, but a Dallas/New England Super Bowl would be the NFL's dream, especially in light of their declining ratings.