This is a really interesting point here. I believe that Jesus was speaking of John as being the greatest man to be born of woman because of John’s position as the prophet with the spirit of Elijah. Indeed the greatest position that could be appointed unto man on this earth. However Jesus then mentioned that he who is least in the kingdom of heaven is greater than he. It sounds like when the apostles were quarling as to who would sit at Jesus’ right and left. Jesus said to them “whoever would want to be the greatest must become like the least”. In other words, the most humble person will be greater than John the baptist in the kingdom of heaven. We all know Jesus Christ is the greatest (Praise be to God!) yet He out of His own will, will dress Himself to serve in the kingdom of heaven.
So after all is said and done the ‘least’ (greatest) in the kingdom of heaven is greater than John the baptist. John the baptist was obligated to fufill his duties which happened to be the greatest duties on this earth. However the position we who are saved take in heaven is left up to us.
PS: There may be a lot of people fighting to get the least position in heaven