Ever since Rorion Gracie forged the Ultimate Fighting Championship in 1993, champions have risen to greatness and fallen just as fast.  Lasting dominance in a sport as unpredictable as mixed martial arts is a rare sight to see.  However, a small and elite class of fighter has proven capable of defying the norm – just look at the likes of Anderson Silva and Georges St. Pierre.  Today, UFC president Dana White aims to please fans by pitting champion vs. champion into what he calls “superfights.” Here are the top five best of the bunch.