Research firm Newzoo recently reported that five games dominated the U.S. PC market in April: Activision Blizzard's (NASDAQ: ATVI) Hearthstone and Overwatch, Tencent's (NASDAQOTH: TCEHY) League of Legends, Epic Games' Fortnite, and PUBG Corporation's PlayerUnknown's Battlegrounds (PUBG).Data source: Newzoo. Chart by author.Hearthstone, a free-to-play collectible card game featuring Warcraft characters, was launched four years ago and attracted gamers with its collectible cards and simple gameplay.