The reason that China have so many good table tennis players is because it is their national sport. This stems from when the emperor a long time ago decided that table tennis would be the official, and essentially only, passtime of China. Therefore it was the only sport that people played. And as such the tradition has kept, just like england's national sport is football, which is why we don't have as many good table tennis players.
However, it is clear to see that even though table tennis is a much more minor sport in the west, europe is home to the best table tennis players in history including Jan-Ove Waldner - the greatest ever player.