On average it takes someone who has gotten to elite level in their chosen field between 5000 and 10000 hours of practice, most importantly during what psychologists call 'critical periods' (basically from birth up until about 8 years old). Take Vanessa May on violin, or Elton John on piano for example.
As humans we are born with one thing that separates us from all other species - language. It's ingrained within us biologically and requires only that - during critical periods - we are exposed to it in order to learn it. Suffice to say, if you supplement that with 'training' (spelling lessons, english lessons, reading etc...) you will become awesome at language - as we all are here.
It's certainly the case that some people are born with a genetic advantage (say, good hand-eye co-ordination, or a fast runner), but the cross-over into greatness would need training. It's the old 'nature vs nurture' debate. It's mostly nurture in most cases aside from language development, to put it broadly and crudely.