Most traditional sports haven't always been considered true sports. When American football was invented in 1869, it was considered a game. It wasn't until 1920 when the NFL was founded that the game of football was officially christened a sport. Basketball followed a similar path, as James Naismith invented the game in 1891, and the NBA was founded 55 years later. It typically takes around 50 years for a game to become a sport.
Today, people who grew up playing Pong now have children playing League of Legends and Call of Duty. History is repeating itself, as video games become electronic sports (or eSports).