Here's a better question: who gives a rat's ass which is more popular? One is a team sport while the other is a combat sport. It's apples and oranges.
I personally don't give a **** if a billion people tune in every weekend to watch soccer or football or basketball or synchronized orgasms or team dog humping. It doesn't matter. None of that - not the numbers of people watching other sports or how many competitors play the other sport - matters. None of it makes mma any less interesting or the other sport necessarily better.
That is not dead which can eternal lie and withs strange aeons even death may die.