Table tennis is a sport that virtually anyone can play, maybe that is why it is so popular. Though table tennis is not terribly popular in the United States, football and basketball take the prize as top sports, table tennis is popular in a great deal of other countries. Table tennis is a sport that once it comes into popularity, it is likely not going to go anywhere for some time.
China is the top country for table tennis because of its accessibility, the fact that it does not take up a great deal of space, and the fact that it does not require a great deal of physical prowess so anyone can play it. Table tennis is not something that requires years of hard physical training and that does not require a huge amount of space making it very popular in Asian nations.
It is also very popular in South Korea which may be in part to its competitive nature. Surprisingly, it is also very popular in Germany as a result of star athletes, Jorg Rosskopf and Steffen Fetzner. Their world championship in 1989 helped make the sport incredibly and it has not lost its popularity since. Sweden also has a very competitive and popular table tennis following and they are working toward dethroning popular Asian competitors as well.