Why is Darwin considered the greatest scientist of all time?

My personal views aside how can people consider Darwin the greatest scientist of all time. So he made one theory about how organisms and species change over time. Newton invented calculus, Developed the Laws of motion, wrote the law of gravity and did the first work in optics. not to mention his little known but highly influential work in christian theology. Or Louis Pasteur who probably saved more lives than anyone in history with his germ theory of disease, pasteurization and rabies vaccine. Or Albert Einstein who completely revolutionized modern physics form the micro universe to the quantum universe. then there's Galileo, Da Vinci, Bacon, Kelvin, Maxwell, Kepler,Copernicus,Faraday,Heisenberg,Rut… (although he was more of a pure math guy than a scientist),Mendel,Thomson,Tesla,Oppenhei… I mean the list go's on and on. even if i believed in evolution this guy would be way down on my top 100 list I mean these people changed the world what did Darwin do. I honestly believe that Darwin is sometimes called the greatest scientist of all time because he is the atheist hero ( which is ironic considering he was a Unitarian not an atheist). Perhaps I am unaware of some of his other contributions in which case someone please enlighten me . I mean it doesn't take an Einstein to figure out that the fast fish survives and the slow one dies.