This is not to debate the greatness and influence of Jesus (p), who influenced my choice for most influential person ever.
The Prophet Muhammad (s.a.w.s) started the closest thing to ever exist that could be called the "Kingdom of God" that Jesus (p) spoke of, had the power of a Caesar and Pope as well as the influence of a Prophet and ruled justly, letting all religions of the day co-exist as long as they didn't break peace treaties (which happened to the early Muslims a lot, people would make peace only to gain a tactical advantage but it failed miserably) and working men pay a tax, Muslims also had to pay a tax that may have been less but it worked and kept the peace.
Within 200 years of his (Mohammed s.a.w.s) death Islam ruled from Spain and N. Africa to China and India's borders, rivalling the once glorious (before Constantine ruined it) Roman Empire in every way, surpassed it in many others.
Europe plunged into the Dark Ages at the same time Muslim Spain was a thriving cosmopolitan area with schools, hospitals, a metropolis of peacefulness that had Cordoba as a jewel of a city as its most important, Europe that is.
Jews weren't persecuted and Christian, Sabaean, Magian(Parsee) all lived with them wherever they existed together in the Islamic Empire.
And it was not a "by the sword" conquest-made Empire, its success was due to Diplomacy and strength, a tolerant system with equitable laws for men and women (Islam) that believes "there is no compulsion in religion" because the Qur'an says so, literally and word for word.
People converted if they wanted and most did but not all, Islam was enough like Judaism, Christianity and even Zoroastrianism that conversion was not a huge change and Islam is easy to practice but has Sufism and other sects with more complex teachings and practices if you wish.
For the time it existed, from the Prophet (s.a.w.s) until the Crusades of yesterday and today's bombings of civilians, before propaganda successfully turned the more gullible against Islam and making it synonymous with evil by fundamentalist fanatics.
And maybe even still:
Mohammed (s.a.w.s) is the most influential person in history.
For the better.
Mohammed murdered Jews at the Battle of the Ditch because they would not support his claim as a prophet of God. M's followers spread the Muslim faith through invasion, pillage and executing those who refused to accept Islam.