Along with what Gerry said about even the personality aspects being heritable, there is definitely a level that dedication can't take you, but talent/genetics can. Even if you take out things like a person below 6ft is much likely to make it in the nba, less obvious stuff exists.
An example came up at dinner yesterday with my brother actually. We were talking about music, and he was dedicated to piano. Playing hours a day, started young, and we had a really good piano teacher. He even went to a competitive college for it. He met people that were a lot better than him, and probably practiced an equal amount or less as him.
No one in our family has played a musical instrument to our knowledge. A few have tried, found they were bad and stopped, so we don't have a genetic component. He probably reached the limit of what someone without the genes for music can reach, and he is really good. Anyone I've met that heard him play will talk about how amazing he was...except those people that went to the college with him, where he met many people better.
Similarly, there are tennis players who have probably put in the same effort as the Williams sisters, until they realized they would not be world champions. And you (if you're not naturally talented) can reach a certain level in your kung fu (as a martial art, not the literal meaning of the word LOL), with hard work, that's leagues above the average person. But still a league behind those who have both talent and determination.