Ah, I was just sitting here going “No one has mentioned Euclid yet?” He basically introduced logic to geometry, and even a chronic math-phobe like myself has to admit that some of his proofs are just…beautiful.
What about Henry Ford? He didn’t invent the car, obviously, but he was the first to really mass produce an affordable, reliable car. Whether you love or hate the automobile, you have to admit it has really changed the world.
Someone in this thread already mentioned Ghandi.
But George Washington was the first since Cincinnatus.
But without Ben Franklin doing all the stuff he did in England and France, Washington would’ve never won the war. In fact, the most important victory - Gates over Burgoyne is the politcial capital Franklin really had to spend in jawing the English and in getting French backing - had almost nothing to do with Washington. Franklin in 1778 already had the Brits offering various peaces that included independence.
I further think that Franklin would’ve had a more likely shot “creating” a Washington (had Washington not been there) - or impelling his countrymen to overthrow the man who would’ve taken the emperor’s laurels in 1783 - than Washington would’ve had finding a Franklin to negotiate in Europe had Franklin not been there.
Similarly, I can believe things would be more the same had Euclid not existed - someone would have come up with mathematical rigor from which the scientific method could follow.
Aristotle.
We can close this thread, now. 
No. George Bush.
He is fucking up the world better and faster then anyone else could. He will go down in history as the American President who fucked it all up (He likes Gadaffi now? Didn’t America hate him 20 years ago and support someone else? Isn’t pick’n’mix favourites a dangerous/stupid way to go?).
What is the point in evaluating brilliant people from the past when one Very Important Person in the present will have more impact on our lives, no matter where we live.
I would put Constantine above Paul. By making Christianity the official religion of Rome (more or less), it increased its popularity.
Bill Gates. Seriously. And the best is yet to come. It may be generations before the ramifications of his accomplishments are truely understood and appreciated.