An old PC game from 1998 that lives on due to its great balancing and continued support from Blizzard.
Frequently ranked as one of the best games of all time, huge tournaments are held every year (I recently watched one in an audience of 200+ people and a professional announcer) and it's nearly a national sport in South Korea.
http://en.wikipedia.org/wiki/StarCraft_professional_competition
This year, Berkeley began a class on the art and strategy of playing Starcraft professionally. You can see the class here:
http://www.youtube.com/watch?v=L7XiE_V0PZ8