Lowest common denominator.
Think about the most populous, easiest to sell to, and most loyal demographic (anywhere, any industry, not just gaming) you can think of, then target it. In this case it's males 15 to 40 who are huge sports fans no matter what (some female gamers too, but it's the same deal). But I wonder if there's a bigger one. What is the most populous activity or interest in the world? Soccer/fútbol? It's why Konami lost it's shit. Gambling? Konami went crazy on that as well. Maybe drinking, but how would you make that into a game? Gun violence? Seems to be covered by dudebro shooting games. Maybe combine some of these? Have a first person shooter that has elements of soccer or American football and gambling; combine all three/four.
Holy shit... I think I invented a new game series. "Shooter League Football: Vegas"