For college sports, they're also the biggest player. The "big" matchups of the week (usually the highest ranked or most interesting teams) in each market are usually played on the major networks that you can pick up with an antenna from the local affiliate. But the rest of the games being televised are carried exclusively* on cable, usually on ESPN channels.
Keep in mind there are 128 Division 1-A (major) programs, and many more 1-AA and lower programs, so there are a LOT of games going on each week. Some games are played during the week, but the very large majority of them are played on Saturday. So there's way more going on then could ever conceivably be carried over the air.
During college football season, there are something like 7 or 8 games playing simultaneously on the various ESPN channels, not including the "Plus" channels that are only available digitally by WatchESPN.
There are a couple others out there (NBC Sports Network and FoxSports come to mind) but neither are bigger in sports than ESPN.
* Depending on where you live, you can also sometimes get radio broadcasts if you live close enough to the school in question that there's a local affiliate that carries the game. Rights for those are handled differently.
when i got my friends to watch the world cup at home i attached a $5 antenna to the DVR (i build a computer with a $120 TV-in card, and had never used until then!)
the image was not the best, but for live sports, who cares?! oh and it got worse every time a plane passed above.
anyway, the antenna was a very easy solution for the impromptu need for live sports.