> There seems to be in fact a very small difference between the aptitudes of the average players and those of the top players

This is an interesting observation across many domains that involve "intelligence". It's actually pretty easy to see why, if you reconsider the scales for "good" vs "bad": The "bad" end of the scale is not at "the village idiot". The "bad" end of the scale is at "a rock". So, yes, once you get from "rock" to "village idiot", "superhuman" is a comparatively tiny step away.

http://lesswrong.com/lw/ql/my_childhood_role_model/