Jefferson I suppose remains as the greatest political genius, at least as far as our country is concerned. Fortunately his ideas and methodology worked and we are here to brag about him.
da Vinci concentrated on more Earthly things, and remains as the greatest 'artist' of that century.
There are arrays of men and women on orders of magnitudes of smart people through out history with amazing historical perspective but there are very few actual 'geniuses.'
There are some that think Michael Moore is a genius.
There are some that think John Kerry is brave.
But there are certain things in history that are absolute and cannot be rewritten.
Einstein regarded James Clerk Maxwell as perhaps the greatest mind.
http://en.wikipedia.org/wiki/James_Clerk_Maxwell
I agree...Newton. The man gave us specific instructions, along with a math he invented to compute the answers, on how bodies in the universe work.
It took Sputnik to prove him right.
Might you include Aristotle as the greatest polymath?
Would you consider Thomas Acquinas as the greatest philosopher/theologian?