I agree with ScottishGuy in that any ethical doctor should make sure a patient's expectations are realistic and show photos of average results. And that their clinics should also publish what their average yield is.
To try and answer your question by defining just what Poor, Average, Good & excellent results, let's take two patients (preferably identical twins suffering from mpb) with average donor density, hair thickness, similar hair/skin contrast and the same number of grafts to cover the same area. Considering both had the same surgeon the outcome of their results could possibly be classified according to such a system of classification.
Poor: pluggy looking, unnaturally low or irregularly shaped hairline, totally visible scalp, pitting, scarring in recipient area, wide and visible donor scar.
Average: small donor scar which is not visible at all once hair grown out, natural looking mature hairline, see-through though natural.
Good: minimal donor scar which is not visible at all once hair grown out, natural looking mature hairline, see-through in harsh light which may be mistaken for slight thinning as it is so natural.
Excellent: virtually indictable donor scar only visible once shaven right down, natural looking mature hairline, only slightly see-through when wet and in the harshest light like fluorescent where it may be mistaken for naturally thin hair as it is so natural. (Only top surgeons have this ability)