The answer
The majority of you guessed right. Either you subconsciously knew the answer, but didn't really know how to explain it or you were sneaky like pyf and did a reversed image search.
Anyhow, the third person has a significantly higher probability of being real (and is real). Here's why:
Hair part
About 95% of men (that have hair long enough to comb on top) part their hair on the left side because that is the side on which their hair naturally parts. The location of a man's natural part is determined by the cowlick, or spiral of hair, at the back of his head. If the cowlick rotates clockwise, the part naturally falls on the left side of the head, and if it rotates counterclockwise, it falls on the right. Although it is rare, some men have two cowlicks, which means their hair naturally parts on either side.
Difference between the two sides of the face
Human faces are obviously not symmetrical. One side is slightly rounder and slightly more expressive than the other. That side of the face generally seems more awake and for about 97% of people it's their left side. That's why most portraits are taken from the left (e.g. Mona Lisa). The trend can also be seen in the poses of pupils in yearbooks.
It's not easy to spot facial asymmetry, but the easiest way is to look at the person's eyebrows, especially if the person is raising their eyebrows or expressing a strong emotion at that moment (happiness or fear). Since the left side of the face is usually a bit more round, the left eyebrow is more arched and higher than the right one.