Always a tough question because the variables that make up great are so many!!! So picking the greatest is not a pure science.
First everyone must understand that a GREAT PASSER is an element of being a GREAT Quarterback, so therefore, being the greatest PASSER does NOT make you the GREATEST QB. Dan Marino could NOT go for a 4th and 1 QB sneak to save his life, therefore he can never be the greatest QuarterBACK.....key ward BACK. He could be the greatest passer though!!
SO with that being said.
My VOTE for overall GREATEST QUARTERBACK would go to hands DOWN IMO
JOHN ELWAY