The one thing you have to ask yourself is am i prepared to do the amount of drugs necessary to make it as a pro bodybuilder. You can put all the genetics, determination and other motivational crap aside and ask yourself that simple question, because that's what it boils down to.
One thing you need to make sure of, isthat you have a plan outside of bodybuilding, ie getting an education, getting some worthwhile work experience, basically setting yourself up for a life outside of bodybuilding, just in case you don't like it or don't make it.
With regard to Lee Priest Cool Col J, the guy hasn't been clean since he was 13. If you recall, he tested postive at the world champs in Malaysia as a teenager in 1991. I too saw Lee Priest as a teenager and there was nothing special in the way of genetics, he was simply prepared to do what it took (ie tons of drugs) in order to succeed.
Whatever you choose, good luck