Tamerlane’s half-assed ranking of the remaining candidates ( now with even more tortured reasoning! ):
#5 - George Washington - As already noted, no single figure was more important in the preservation and eventual success of the American Revolution. Moreover he set the mold for the U.S. presidency and arguably was the single most influential leader in U.S. history. No small thing, considering the impact of the U.S. on the modern world has been enormous and it stands today as the lone superpower in the early 21rst century.
However…While GW was the single most important figure in the AR, the fact is credit here is shared with many. It was not GW that wrote the Declaration or the Constitution, nor is he the man behind many of their philosophical underpinnings. . He’s #1 in a cast of many and his individual standing drops a bit as a result.
Moreover the U.S. is such a very, very young state. Enormously influential in modern history? Yes. But Johnny-Come-Lately in the whole pageant of human history.
Also he started losing his teeth in his twenties and used dentures with horse and donkey teeth. Gross.
#4 - Alexander the Great - He is the single greatest archetype of the world conqueror in history, rivaled only by Genghis Khan - the Macedonian conquest of Achaemenid Persia and beyond was truly an astonishing feat. And he was the herald of the Hellenistic Age, which spread Greek culture from the Mediterranean Basin to western Central Asia and northern India. His Greco-Macedonian successors dominated this huge region for centuries ( culturally at least, for a period longer than the U.S. has been in existence ) and significantly influenced the rising young Roman Republic along the way.
But…his dynasty did not really survive him in a meaningful way. Hellenization, even in Asia Minor, ultimately proved ephemeral in the fullness of time. And Rome, while it hero-worshipped Alexander, would undoubtedly have been pretty heavily influenced by Greek culture even without him.
Also, he was simply an incredible prick of a human being. The worst of this remaining lot, easily.
#3 - Caesar Augustus - Creator of the Roman Empire, arguably the most important state in western history in many ways. Even aside from this accomplishment, he probably is in the running for greatest ( most capable ) emperor period and that’s a category with plenty of serious competition. A genuine genius.
But Augustus started with a huge, huge advantage. He “inherited” the empire of the Roman Republic, already the superpower of its time. He reformed and reshaped it, but he did not create it.
Also he treated his first two wives, especially the second, Scribonia, kinda crappily.
#4 - Qin Shi Huang - the creator of “Han” China ( okay the Han created Han China, but he created what would be Han China ), through all but 19th century-today ( plus a few other very small blips ) the wealthiest, most sophisticated, most educated, most technologically advanced, most enduring, most powerful state over the full, cumulative span of post-agricultural revolution world history.
And the Terracotta Army - that’s probably about the coolest thing ever!
However, while he didn’t start with as massive an advantage as Augustus, above, he started with a big one. His Qin state was already the dominant power amongst the Seven Warring States. He more or less built on the achievements of his predecessors and completed a process that was already moving semi-inexorably in the direction of consolidation. And his dynasty, like Alexander’s, barely survived his death.
Also he was a book-burner ( and a burner of scholars that tried to preserve certain books ), one of the nastiest sins imaginable.
#1 - Cyrus the Great - Why? Because he started with the least and established the most from that start. Persia was a very minor, backwater state at his accession, more or less covering the southwestern fifth of modern Iran. He built it into the mightiest state ever seen up until that point. Not only did his dynasty ( through various branches and not to be confused with states ) out last any of his competitors above by an enormous margin ( ~220 years ), but he established another of the great cultures of world history, out of almost nothing.
The Seleucid dominance was short-lived and replaced by the Perso-centric Parthians, who along with the their successors the Sassanians created the only great state to consistently compete with and block Rome. It was sheer luck the Arab eruption happened at a time of devastating weakness. Even then Persian culture, now Islamized, triumphed in the end. The Abbasid Caliphate was a thoroughly Perso-centric state. Persia and Persian has endured where other classical societies ( like Egypt ) have not.
And it all pretty much stems from Cyrus.
Also the Jews tend to like him.