More like 90 minutes. It depends on how much interest I have in what the announcers are saying and what's going on before the snap. If I really care about which two receivers are wide to the right, or I want to see the eleventh angle on a replay to determine if a ball was caught or trapped, I'll watch the broadcast and just zip through the commercials. If I just want to see the plays themselves, it could probably be done in 30-45 minutes.
Each team runs an average of 75 plays per game. That's 150 plays at, what? maybe ten seconds per play. That's 1500 seconds of actual football action, or 1500/60 = 25 minutes. Of course, you'd need to have hands like a surgeon on the remote control, and it does take some physical time to fast-forward from play to play, and through the commercials. 45 minutes is a realistic minimum.
My DVR has a “skip forward” button that moves 30 seconds ahead. That is about the time it takes from a tackle till the next snap, unless a team is running hurry-up.
About 90 minutes to watch a game. Zapping through all of the commercials and official reviews is priceless.