Two top leaders of Cambodia's Khmer Rouge regime were found guilty of genocide on Friday, in a landmark ruling almost 40 years after the fall of a brutal regime that presided over the deaths of a quarter of the population.The Khmer Rouge's former head of state Khieu Samphan, 87, and "Brother Number 2" Nuon Chea, 92, are the two most senior living members of the ultra-Maoist group that seized control of Cambodia from 1975-1979.The reign of terror led by "Brother Number