A good song writer may be a matter of opinion but I think an open mind in terms of being willing to welcome inspiration from all sorts of experience both musical, imaginary and personally real. There is also a question as to whether one good song constitutes a good songwriter. I think an ability to write in a number of styles , perhaps unaccompanied and with different instruments, may be quite important to an overall assesment of a songwriters talent. Overall I think the songwriters art is typified by the ability to express complex stories, ideas or emotions in a very concise fashion.