well yes, its mostly based on genetics.
but here are benchpress exercises that might help you understand what muscles are worked
decline bench - lower chest
flat bench - middle chest
incline bench - upper chest
wide grip decline bench - outter lower chest
wide grip flat bench - outter middle chest
wide grip incline bench - outter upper chest (near shoulders)
flyes (the valley maker as you would put it)
inclined flyes - upper inner chest
flat flyes - middle inner chest
decline flyes - lower middle chest
hope that helps ...
just dont do them all on one workout .... split it up.
but your genetics will be the main factor ... look at any 3 guys chests and they will all be different.