I think FredPuli is rather complicating the matter. A "far cry" dates back to the pre-mobile days when the only way of communicating with a neighbour was to shout to him, and meant that one place was a long way from another. (A corresponding term of nearness was "within cry of".) In time, the expression began to be used metaphorically, to refer to any two things which are related but a long way apart, such as "Tony Blair's current popularity is a far cry from the glory days of 1997".