To me, martial arts is about taking what your student has, and developing it as well as you can. For example, there are some students, due to the absolute lack of flexibility, who will never be able to kick above the waist, or students who have significantly less mobility than your "average" student. This does not, however, preclude a student from becoming good at the martial arts, since it's not just about one technique or ability.
How a sensei can bring out the best in each person who may be lacking talent, can often be seen as a good measurement of his teaching abilities.
Talent, though, does help, and of course, it's a joy to have someone with both talent, and the work ethic to go along with it. If anything, such individuals can indirectly help a huge amount, since many of the others will aspire to be that person.
Talent alone, still won't get you very far in professional sports, such as the NFL. Maybe in high school, but probably not in college, and definitely not in the pros. I've seen quite a few talented high school players stagnate horribly once they hit the college ranks, because their coaches were inept, and were unable to develop them. Either that, or they refused to listen to instruction, and fell by the wayside.
Some are even given a second (and third, and so forth) chance, and blow it:
Take a look at the Ohio State University runningback, Maurice Clarett:
http://en.wikipedia.org/wiki/Maurice_Clarett
The kid was a football god (awesome talent) coming out of high school, had a remarkable freshman season, but then fell by the wayside horribly. He was even given a golden opportunity by Mike Shannahan (Denver Broncos coach), who has always been a great evaluator of talent, and blew it.