If the mid-point between one handed and two handed is a "bastard" sword, then I propose we call the mid point between Longsword and Greatsword the "Promiscuous Husband" sword.
This is why in RPGs, I would have any character carrying a great sword attract some very funny looks - where a longsword would be like openly carrying a pistol (which is more acceptable in some places than others), a great sword would be like openly carrying an LMG...
i believe in Italy great swords were used for "self defense" in that a person would have a body guard with one on his shoulder. In those day i think it was common to be jumped by like 4-6 guys with daggers and rapiers, and nothing says fuck off like a big swinging death pendulum
In my mind it has always being the point at around half the video, the defining factor: if it can be draw from a scabbard at your belt it's a longsword. If it needs to be carried like a polearm it's a greatsword...