There's actually a book on the subject:
The 100: A Ranking of the Most Influential Persons in History by Michael H. Hart
Top 3 were: 1. Muhammad 2. Isaac Newton 3. Jesus
http://en.wikipedia.org/wiki/The_100:_A_Ranking_of_the_Most_Influential_Persons_in_History#Hart.27s_Top_10_.28from_the_1992_edition.29