Most Helpful Guy
A lot of it is symmetry. That is both sides mirror each other. The eye can pick up on it and it tells our brain which person would be better to mate with to have offspring that would have a better chance at surviving.
Keep in mind that you won't be a perfect 10 to everyone. If you have a round face, guys with round faces won't find you attractive. It is because their brain is sending a signal that you have too many features they have and are possibly related to them.
I have an elongated face, my jaw line is rather thin and I love love women with round faces. I thought it was more because I am German and Germanic/Russian women have round faces but low and behold it was something different.
You can do a few things to increase your point total a few tenths of a point but ultimately you can't mess with genetics.