Basketball isn't a 'black' game, it's a 'city' game.
Whatever 'group' of people make up the majority of the population of the inner cities (particularly the inner cities of the northeast) has always been the dominant force in basketball.
In the 1920s and 1930s, it was said that every Jewish kid was born with a basketball in his hand. The reason was that inner cities were predominantly Jewish, and Jewish players dominated basketball.
Around that time, the Jewish inhabitants of the inner cities began to move out of the 'projects', and Blacks from the South moved into these same projects. Blacks then became the dominant force in basketball, and have been dominant ever since.
Blacks have historically spent a lot more time at the courts than whites have, as well. Even today, while white kids are more likely to spend their lives playing video basketball via NBA 2K6 (or whatever the latest version is), blacks tend to actually get out there and knock heads on the basketball courts in the neighborhood.
Blacks, as a rule, just work harder at it, but the blacks who make it to the NBA get there because they are not only superior to whites, but they are also superior to other blacks as well.
It takes hard work and practice to become 'good' at anything. And anyone can become among the best if they work hard enough at it...Larry Bird was the best player in the NBA (along with Magic and Kareem) from the minute he stepped on the floor... but behind the superstar rookie lay thousands upon thousands of hours of practice.