The problem with games like League & DotA is they're nearly impossible to understand what's going on as a spectator unless you already play the games. They're a victim of their own complexity - over 100 characters each with a minimum of 4 unique abilities. It makes major fights practically impossible to follow as a person who doesn't play the game.
SC2, on the other hand, is much easier to grok as a spectator. It's 1v1, so you know each army is controlled by 1 player, and the capabilities of the units are far more obvious as well, since a lot of them are based on pre-existing science fiction concepts.
League & Dota get far more viewers because the games are far more popular, however, as a spectator sport, they fall short because of their complexity.
SC2, on the other hand, is much easier to grok as a spectator. It's 1v1, so you know each army is controlled by 1 player, and the capabilities of the units are far more obvious as well, since a lot of them are based on pre-existing science fiction concepts.
League & Dota get far more viewers because the games are far more popular, however, as a spectator sport, they fall short because of their complexity.