Watching gamers play video games online is becoming a major growth market. That's why Amazon bought Twitch, the world's most popular video game streaming platform, for $1.1 billion in 2014.

Between 2014 and 2017, Twitch's unique monthly viewers grew from 100 million to over 140 million. The platform has 2.2 million broadcasters. Fifteen million people watch content on Twitch daily, spending an average of 95 minutes. These were the top five games they viewed in June, according to Newzoo.

Chart showing the five most watched esports games on Twitch.

Data source: Newzoo. Chart by author.

Three companies dominate that list. Valve publishes Dota 2, one of the world's top multiplayer online battle arena (MOBA) titles, and the first-person shooter Counter-Strike: Global Offensive.

Tencent's Riot Games produces League of Legends, Dota 2's top rival in the MOBA space. Activision Blizzard publishes the popular shooter Overwatch and the online card game Hearthstone.

All five games are easy to understand, making them ideal for esports competitions. Newzoo expects the number of e-sports viewers worldwide to grow from 380 million this year to 589 million by 2020. It also expects the market to grow 38% to $906 million this year, with sponsorships, advertising, and media rights generating most of that revenue.

John Mackey, CEO of Whole Foods Market, an Amazon subsidiary, is a member of The Motley Fool's board of directors. Leo Sun owns shares of AMZN and TCEHY Holdings. The Motley Fool owns shares of and recommends ATVI, AMZN, and TCEHY. The Motley Fool has a disclosure policy.