Depends on your measure of success. Hong Xiuquan was a peasant from Guangxi in southern China who received a series of visions, which he later interpreted as revelations that he was the younger brother of Jesus Christ, sent by God to rid the world of demons. After a few years of preaching, he had tens of thousands of followers, and after routing an Imperial army sent to disperse them, he declared himself the Heavenly King, and stormed the southern capital in Nanjing. Over the next decade, their ranks would swell to hundreds of thousands of soldiers, ruling over perhaps tens of millions along the Yangtze river. He was ultimately killed and his kingdom reconquered, but it was after years of hard fighting and intervention by Britain and France.

Muhammad was a common man - he only gained power after starting his movement. He was a member of the ruling tribe, but that tribe was massive, and he was not a particularly important member of it. In fact, he married up, one could say. His first wife, who was significantly older than him, was a successful trader (perhaps the widow of one? I can't recall), and it is through this relationship that he gained some measure of influence, allowing him to amass followers.

Granted, the religion is not centered around Muhammad in the same way as Christianity is centered around Jesus, but that's only because Islam is extremely monotheistic and Christianity is only weakly so. Suffice it to say though, the importance of Muhammad to Islam is comparable to the importance of Paul to Christianity. Without either, the religion we would end up with would be very different from the one they passed on.