The chart below looks at five-year periods in NFL since the 1978-82 period and how much the two best teams dominated during the five-year period. Their dominance is measured by the average number of wins those two teams achieved during the period; playoffs wins are included. For example, if Dallas won 60 games and Denver won 50 games during the five-year period, then the chart would read 55.
The ‘Boys and Niners were the most dominant until Brady and Manning surpassed them in 2007.