@Elmud,
I think Sarathustra raises a very good point. We probably have no knowledge of history's greatest genius.
The first person to wear clothing?
The first person to cook food?
The problem seems to me that in choosing a 'most influential person' people tend to choose a magesteria (eg: religion, military, politics), and then just choose their favourite person from a list of those associated with that group.
It says more about the proposer of such a list who they choose rather than history, I think.
So a Christian who believes the Christian religion to be the most important thing about life might choose Jesus, or Adam, or Abraham.
However, such people do not strike me as particularly influential. Firstly I personally doubt they even existed, and secondly what did they matter to most people throughout most of history. Does what Abraham did influence Hindus? It's irrelevant to most of them surely?
I think two things make human experience very different from that of other forms of life as far as I can tell, they are:
1) Invention of tools.
2) Use of language.
So I would propose Archimedes and Shakespeare as the most influential people in history because to me they represent the epitome of what it is to be an inventor or an eloquent user of language.