Parity is "the state or condition of being equal". Perfect parity would be a new team winning every single year. In your example, you are looking at the national championship winners since 2009.
In statistics, the way we typically quantify how equal everything is in a data set is by the standard deviation. I'm going to calculate the standard deviation for you of three cases:
1. A season of perfect parity (new team wins every single year) - standard deviation of zero.
2. Football results since 2009 - standard deviation of 1.76.
3. Basketball results since 2009 - standard deviation of 0.89.
Basketball has WAY more parity, and it's not even close.