I think you have a poor question as in reality its a combination of all of this.
You'll have those purely lucky on the basis of being born into the right family. Those are people like royalty and such.
Then you have those that had that lucky family and did enough work to keep it going and even grow the wealth. These people have some luck as well as some basic work. Someone like Paris Hilton fits this category. She has wealth and was able to get into the right crowds with her family, but she has done enough basic work to continue that trend. (tv acting and marketing of herself)
Then you have those that really demonstrated concentrated effort to get to where they are. I think your examples as well as those shown by others clearly fit this. M.Jordan (as well as most other sport greats), M.Jackson (as well as other great artists), B.Gates (as well as many other great business people).
These people all have some basic raw talent, but also worked very hard to achieve greatness. It wasn't handed to them. M.Jordan would not have been able to get 6 trophies in NBA, countless other awards, NCAA trophies and awards, known as a fiere competitor, by far the most business deals of any sports person (only one to still have full clothing after retirement), etc, etc... without a lot of very hard work.
M.Ohr is a bad example as there are plenty of top athletes from the ghetto that are worth a lot.
I could continue with many other examples, but to generalize it as you did is really not fair to the great number of those who have worked their assess off to get where they are.
