Yeah I think when you take into account that you have to "be a fighter" to even enjoy MMA, compaired to literally every kid in Europe playing football as a youngster (and Brazil has much more passion for football than we would), it will just never take over.
The only real sports MMA can be compaired to would be like kickboxing, boxing, judo, karate and other martial arts. A lot of people like to combine it with WWE, but the only reason that they are together is because WWE is genius with their marketing and are completley capitalizing on the MMA boom just like they did with boxing in the 90s. Pro wrestling will appeal to children always, while MMA is an almost exclusivley adult show.
I'm just waiting for the day that UFC takes over boxing in PPVs. Once we lose the likes of the Klitschkos, Mayweather and Pacquaio, there is a chance that guys like Jon Jones will bring MMA into a new era. We just need more modern day legends because it wont be long before we see the back of Anderson, GSP, Vitor and all the other big name legends.