I consider myself one that's very good, but I look at people like Carmack and realize I will never be one of them...that won't stop me from trying to though!
That said, I don't contend that some people are not at some point 10 times more productive than others. I contend that anyone can be just as productive, and often are, were or will be, although the manner in which they should be productive is absolutely not clear-cut. Society as a whole shapes how we act. Diversity in its composition allows what we rely upon.
For instance, I would not be as productive at work if I had to take care of a few children on my own. Similarly, I am extremely unproductive while gardening, and don't intend to spend the time to improve.
That seems to either be such a strong claim that it's trivial to refute, (i.e. a newborn baby, or a quadriplegic with severe mental retardation, etc.), or too nebulous and ill-defined to be of any use (i.e. said quadriplegic is productive in cultivating character in carers?)