Esports & PC on Top
Four PC games, League of Legends, Counter-Strike: Global Offensive, DotA 2 and Hearthstone, are litterally dwarving the competition on Twitch. If we were in NCAA basketball we'd call them the Big 4 or something. And among the Big 4, there's the BIG ONE: that's League of Legends of course, watched almost twice as much as its closest competitor.
Why these 4? Why so big? Of course esports come to mind as these 4 games are the biggest Esports platforms out there. What the numbers seem to show is that esports can generate tremendous passion among those who get hooked, which then leads to major live viewership peaks.
Last August, Twitch broke its record for maximum concurrent viewers on the platform at 2.1M, precisely at the time when the finals for ESL One Cologne and the North American LCS Finals were both being streamed. In this regard, esports are very much like regular sports on TV: they allow the biggest live viewership boosts.
Outside of the Big 4, 2 other games in the top 10 also got there for the most part because of esports: Starcraft 2 and Call of Duty. Call of Duty, by the way, is the only game that's not exclusively for PC or PC-centric out of those 6.