The one-eyed man

I heard that this expression means a person who is not very smart but he is the best among his crowd already. The story is that all other people in a place are blind and therefore the only person with one eye became the king. Is the above true/correct?

Quoteland.com attributes the quote as follows:

"In the kingdom of the blind, the one-eyed man is king."
-- Desiderius Erasmus (1466?-1536), Dutch humanist), Adages

There was (in the '60s if I remember correctly) (insert '60s memory joke here) a wonderful little satirical magazine which unfortunately didn't last long, who used this quote as its motto. The magazine was called, of course, Monocle.