Which genes are good and which ones are bad? Which genes make a symmetrical face for example?

The bad ones.

The square ones of course. The others are just junk.

The general public easily recognises the faces of people with Down’s syndrome, but there are over 700 genetic conditions where there are characteristic facial features: the eyes may be set further apart than usual, the nose shorter and the ears set lower down on the head along with many other possible permutations.

http://www.sciencedaily.com/releases/2007/09/070910093354.htm

I'm not certain that you can necessarily class genes in terms of good and bad.
http://en.wikipedia.org/wiki/Gene
The gene that causes sickle cell anaemia for example is "good" as it imparts a certain degree of resitance to malaria - but bad because it shortens overall lifespan.

http://en.wikipedia.org/wiki/Sickle_cell

Certain "bad" genes like the one that causes huntingdons are recessive, so are only "bad" when an individual has 2 copies of it - if you only have one its neutral.

http://en.wikipedia.org/wiki/Huntington%27s_disease
http://en.wikipedia.org/wiki/Recessive_gene


Its also possible that a previously deleterious gene mutates into something useful.

http://en.wikipedia.org/wiki/Gene#Mutation

there isn't a gene that codes for a symetrical face, as no-one has a symetrical face (are you Happeh in disguise? :) ) - but in terms of which genes are responsible for the development of your body, these are called HOX genes

http://en.wikipedia.org/wiki/Hox_gene