Has any guy ever chosen Ginger? Deep penetrating intellectual discussions on this topic over a pint at the pub suggest the answer is no.
But it's more than looks. Consider: Mary Ann is a regular, down to earth modest (in dress and temperament) midwestern, and therefore conservative, girl. Ginger, being an eccentric actress is obviously liberal (she wouldn't like FR).
Now if I were Gilligan....
I remember being a teenager when the series first came on and thinking how tough it would be to live on that island the way the castaways did (sexless aparently except for the Howells).
The show is actually incredibly stupid but I watched it anyway just to see Mary Ann in those short shorts.