I think what is making it look a bit "alien" like, is the jaw bone. You have it way too deep, making it look like the back of the head is "growing", typical of alien designs.

Its definently getting there mate! Don't render it out too soon though becuase we can't really see what it looks like.

Also, it helps to assign a blinn material onto the mesh to make it easier to spot imperfections.

Cheers mate!