My two Cents---- Leadership is the ability to influence. In terms of bad or good influence. How can you classify someone as "a great influential person" when there values are bad or ignorant. In this case "Hitler" or "Osama bin ladin"? I wouldn't even call them most influential -- simply because there ideas and leadership was halted and doesn't effect our ideas of living in present or future. Example both Oprah Winfrey and Bill Gates have more influence to shape our history.
I know many great leaders in the military (people I would sacrifice there lives for). Being a military leader is not as "constructive" as being a civil leader --- because the military is designed for leadership and demands influence based on position. Civil leaders are more influential on there actual ideas....Alot of great names are not being mentioned.
Abraham Lincoln -Civil War era President who abolished slavery
Martin Luther King Jr - Anti-segregation activist
George Washington - independence leader, first President of the USA
Sir Winston Churchill - World War II-era Prime Minister
Galileo Galilei - Founder of modern science
William Shakespeare - Legendary playwright, director
Nelson Mandela - South Africa's first black President, anti-apartheid activist
Albert Einstein - Scientist, founder of theory of relativity
Mother Teresa - Catholic nun, child poverty activist
Isaac Newton
Caesar
Genghis Khan
Michelangelo
William Shakespeare
Ayn Rand
Alexander the Great
Plato
Karl Marx
......list goes on and on.
To answer your question though........most of the "GREAT" leaders mentioned above were influenced by the the greatest man ever to walk the Earth.
Jesus Christ. -- 33% percent of the population today is classified as "Christians"
I can go on for days about his influence on people --- I'm a personal testimony.