I don't know actually, because though I have some friends who look good when they smile because they have one or two dimples, I also have a couple of friends who do not smile at all in photos because their dimples make them look odd. And I agree with them because both of them (though they do not know each other) have dimples just below the eye area. And it somewhat looks odd when they smile.
However, there are a lot of pretty faces that do not have dimples.