I am not sure that current leaders such as League of Legends or Counter Strike - GO will be on the top because they don’t meet requirements for a true spectator sport.
A good spectator sport must be easily understandable by people who don’t practice it. For that to happen, it must be slow enough so spectators understand what they see.
Second, someone that does not know the game in details must be able to appreciate players’ accomplishments; you don’t need to practice basketball to appreciate the beauty of a dribble or a distant shot.
Third, a spectator should be able to get a global view on what is going on; that’s why it is more rewarding to watch a ball game in the stadium than on TV because you get the global tactical situation.
Clearly, most games used in eSport today don’t match those requirements. If we want eSport to become mainstream entertainment, games must be designed with the audience in mind.
Games that meet those requirements are adaptations of existing games like soccer or tennis. Could they become the next eSport references? Probably not because of competition from their real-life counterparts.
I think the winners of eSports will be games that offer a mix of situations spectators could relate to and the kind of fantasy only video games or movies can deliver. A few years ago, I was working as lead level designer at the Ubisoft studio of Annecy where we developed the multiplayer modes of both Splinter Cell - Pandora tomorrow and Chaos Theory. Stephane Faureau, who was the studio manager at that time, had the vision of using our multiplayer game for eSport, which was barely emerging.
Why did he think so? it is largely because of a brilliant idea implemented by Ubisoft marketing staff: For the release of Splinter Cell - Pandora Tomorrow, they organized in the US a competition between the East and West coasts. In one local theater on each coast, teams of two players were competing against each other. Our multiplayer game mode was based on asymmetric gameplays: Spies were stealthy but poorly equipped for combat while the defenders, named mercenaries, were clumsy but enjoyed heavy weaponry and good detection equipment. In spite of its complexity, the cat-and-mouse game was easily understandable by an audience that did not know the game because it had not been released yet. The enjoyment roars of the audiences showed us that our multiplayer mode had a real potential for a spectator sport.
I believe that we discovered, without realizing it, key design features of what could become true electronic spectator sports.