Online games are big business, and now players are making real money and becoming stars at it. In South Korea, at least a quarter of the population has participating in a game called Kart Rider. “Kart Rider competitions have been broadcast on two cable channels, and Kim Hyun Wook — who has won several of them — has emerged as a pop idol among gamers. A local apparel company, Spris Corp., sponsors Kim and three others as professional Kart Rider players. Some tournaments have been sponsored by the likes of Coca-Cola Co. (KO ) and offer as much as $50,000 in prize money.