Surprisingly Abraham really did nothing important in his life.  He was not a great writer, king, inventor or military leader.  He did nothing except camp out where he was told to go and father a few children.  His name is great only because the children became nation(s) that kept the record of his life – and then individuals and nations that came from him became great.  This is exactly how it was promised in Genesis 12 (“I will make you into a great nation … I will make your name great”).  No one else in all history is so well-known only because of descendants rather than from great achievements in his own life.