UFC (Ultimate Fighting Championship) has had phenomenal success since it's first match in 1993. Especially by attaining deals with cable networks and as pay per view, UFC has become of the most exciting and watched sports of the modern era. The scariest part about UFC, aside from the arm bars, the crazy knee kicks to face, and the gore and blood that ensues, is that it is continuing to surge in popularity.
Just recently, UFC set a record for viewership in prelim fights (which is a record itself had actually owned previously) according to the Examiner. http://www.examiner.com/mma-in-las-vegas/ufc-sets-record-for-prelims-on-spike-tv
What is so fascinating about UFC that it is continuing to captivate viewers around the world, especially despite the fact that most of its broadcasts come at the extra cost of pay per view? This is because UFC is so drastically different and realistic from any other combat sports we have seen so far. Most fighters who compete in UFC are mixed martial artists whose backgrounds in martial arts is not limited to one area (like traditional matched of judo or boxing), but a mixture of strangely named sports like Brazilian jiu jitsu, muay thai, and Greco-Roman wrestling.
UFC's goal from the beginning was to broadcast shows that would exhibit which martial arts would be the most effective in a real fight. So unlike WWE/WWF, this would be real world, nitty gritty stuff. Something about violence is fascinating to people, therefore we submerge ourselves in slasher flicks or play violent video games. With UFC, viewers are even more engrossed in this world of violence because it is actually real (in some ways like our fascination with other violent sports like football). Professional boxing was probably one of the closest martial arts to come to the level of popularity and attention that UFC is currently having.
Watch it for yourself
Whenever I watch UFC fights, I always instinctively cringe and shout out, "Ooooohhhh, that musta hurt." Then I continue to submerge myself in the blood and the brutal fighting that ensues. Something about it is mesmerizing and captivating. Best of all, it's so... real.