Here's the thing, its the same length as an NFL game. If it were 10, maybe 8 minutes, and a mistake wouldn't lose you the game, it'd be a lot more interesting and fun.
So, I have a few ideas. First, the one I'm leaning to, and a forum I started before I revamped the jerseys recently, a U.S Cricket League dating back to the 1850's. Second, a mix of International Football (Gaelic and Australian) and Rugby