There are way more teams - over 350 to be exact - in just Division-I alone, and a large chunk of fans actually got to attend the schools they root for, or live/lived near the campus. While the NFL has more of a global reach, it could be argued (probably not well though) that college football has a larger fan base across America.
There's no contest that the football - as in both the NFL and college football - rule sports in the United States.
