Maybe as well as having 11 different games you could also require say 8 (just an example) different game types, that way somebody who only plays chess and variants, for example, would not be included on the list.

On a side note, I think it is mostly chess players who skew these results as there are so many variants of chess that you can make the list without knowing any other game types. This is not the same for a line game player or reversi game player as they have to be good at someother game type other than their "main" game because there just arent 11 different game variants for those games.