League of Legends el año pasado estaba en segundo lugar con 624 millones, este año llego al primer lugar con 1 billón.
Todo gracias a microtransacciones con un modelo free to play, sin que sea pay to win. De hecho pagar no te da ninguna ventaja en el gameplay.
Muchos critican al LoL pero la verdad están haciendo las cosas muy bien.

Microtransactions. "Micro." As in, very small bits of money—a dollar here, a dollar there—exchanged for comparably small in-game items: A new hat, perhaps, or some healing potions. But boy, it sure adds up. Riot Games earned $624 million from League of Legends last year, and that was only good enough for second place on the top-ten free-to-play earnings list. In 2014, however, it's shot to number one, and is poised to be the first to break $1 billion in microtransaction revenues.
http://www.pcgamer.com/league-of-leg...otransactions/