I have been away for some time, but I do want to reply carefully to you (and respectfully too), firewalker99.
Let me give my first impression of you: you are one of those people who I would classify in the "being a duped optimist" category. Let me calrify that clearly. What you have said about scientist doing all this research to prove this and that is meaningless to me - it's superflously extraneously pointless even. It makes for good copy for newspapers like the Daily Mail to include so people can read it and feel good that they too have a chance. This kind of "crap" is everywhere, and it's not just in the area concerning aquisition of wealth/status/power.
Let me take the area of self help, particularly relationships, where women's magazines are full of such superflous crap about making the most of your life/how to meet the perfect man etc. . . In that area I would fit you in the camp that believes anyone can get anyone to fall in love with them if they know how to act/behave properly, and it has nothing to do with looks. We are entering a grey area here, but I think we can all agree - I hope we can anyway - as mature adults that we are very selective as individuals when it comes to who we are attracted to and who we are not. I am not saying it's all about looks, nor all about personality, but there are people who - no matter what their personality - you are just not attracted to, and vice versa and every other combination of factors and effects in between. What I am saying is that there is a sexual selection process happening. It may be utterly brutal but it is happening. In this area you would be the kind of guy who would expand the theory that it's just to do with confidence/knowing what to say/wearing the right clothes/create the right demeanour of an alpha male and all that crap etc, etc, . . . whereas me and socrates would be saying that you can't create attraction, it's either there or it isn't. We would be saying that you can't get such and such a girl because the brutal fact of the matter is that she's not interested and it's her decision, in the same way if someone showed an interest in you who you are not interested in it would make you feel sick (this happened to me by the way, I did not know the person in question but physically she was not my type and hence I was not interested).
Now lets go back to the point:
Why doesn't he has it? I don't know much about tennis, but I do know about Formula 1. Why are champions like Schumacher and Senna a class of their own? Because they are fanatics. They work like mad, train like mad, drive hundreds of test laps more than others and got started very early in their life (driving karts on the age of 4 or 5). Every other driver in the field admitted that Michael Schumacher worked extremely hard in every aspect of his career, not only on the track but also off the track. Again, hard work seems to be the key here!
if it was all just hard work then anyone can do it, provided that they can take the pain. But I would hazard a guess that your way out of the argument is that there is a selection on individuals who have the genes to work hard/drive themselves forward/put in fanitical effort, then that would still have the "born with it" argument valid. This is not the case, because if it were true History would not say that "Schumacher and Senna" were great drivers, History would just say they were the "hardest working drivers" and that's why they kept on winning. Could anyone believe that? Don't think so.
There is a brutal maxim in History that says that "history is written by the winners". Let me clarify with an example. At the time of Einstein's success there were individuals who worked harder, if not more harder, than him, on their own ways of explaining the ether effect etc . . . . We do not hear of them simply because they were not the winners, their work/theories were minor landmarks in the progress of science, Einstein dominated. He had what it took - whatever it was, and I still doubt that science can every find that out in our present state of ignorance.
In your quote you ask why can't Tim Henman make it, and the answer is simply because he doesn't have it in him. He has it in him to make the grade, be in the top 5, but not enough to win a grand slam (unless all the other players die off, get food poisoning, injured etc. . ). I am sure he works just as hard, if not harder, than Sampras, but he just doesn't have it in him. I've seen him play again Carlos Moya (French Open Champion), and you can tell that Moya has that something extra, just that edge - and no amount of practice can make up for that.
Another example is the mathematician Karl Frederich Gauss, in his late teens he proved the quadratic reciprocity law. His professors at the university of Gottingen have also been trying to do it (so had Euler, Legendre etc . . ) and failed. And these guys had spent a good part of their lives trying to, so it wasn't for want of work or practice, and then comes this upstart boy that puts them to shame - think of the jealousy and aggression they must feel. Einstein in later life would also comment on other scientists aggressive jealousies towards him.
The point I am making about Newton working hard is that once you start doing something you like, and have serious talent for, you will find that you enjoy it and hence spending manhy hours on it is a pleasure and it gives you a buzz, you cease to see it was work more like a hobby, something you really want to do.
This is the first part, I will add a second part later on pending your reply.
I have to say now that I bear no ill to Socrates, and am very sorry about how I initially treated him. He actually does mean well, although most people don't take it that way.