Study has shown that the most attractive face is the average of the general population.  This is done by having test subjects identify the attractiveness of artificially generated images –   morphed together by averaging photos of many different people.

The earliest known experiment dates back to 1883, by Francis Galton, cousin of Charles Darwin.  Recent research in 2005 by imaging researcher Pierre Tourigny using photos on HotOrNot.com also shows similar results [Image on the left].   For a detailed explanation of the images, click here or here.

The averaged photos tend to cancel out blemishes, and balance the symmetry of the facial characteristics.  This is inline with a recent study where people finds symmetric faces to be more attractive.

Link: http://en.wikipedia.org/wiki/Averageness