Blizzard has been the king of online PC gaming for years, but thanks to largely self-imposed wounds, it could be unseated by Riot Games — Ever since Warcraft, Diablo and Starcraft established themselves as leaders in their respective genres, Blizzard Entertainment has held a captive audience of millions, who devote endless hours to their titles. World of Warcraft, with its many, many expansions, is one of the highest grossing PC games of all time. …