2. League of Legends
I've got friends back home who are addicted to this. The guy in the adjacent room in this San Francisco house we all share constantly moans when he plays, frequently yelling "the LAAAAGGGG" when he really just sucks. I haven' t touched League of Legends, but I can't deny its popularity and its sway over its loyal fans. Inspired by the Warcraft III mod, Defense of the Ancients, League (or LoL as some…people have called it) has made free-to-play a viable business model and made the MOBA an e-sports stalwart.
Countless free-to-play imitators have sprung up and Valve's direct competitor, DOTA 2, has skyrocketed in popularity since its inception, but League of Legends is the the model by which all other of its ilk will be judged for now due to its quality, non-invasive free-to-play model, and its ability to compel gamers to keep playing.