Some of you may find this list interesting. I looked up a current list of the 10 most popular games on Steam and here is what I found:
CURRENT PLAYERS GAME
894,772 Counter-Strike: Global Offensive
646,298 Dota 2
574,274 PLAYERUNKNOWN'S BATTLEGROUNDS
226,668 Grand Theft Auto V
180,463 Tom Clancy's Rainbow Six Siege
158,341 MONSTER HUNTER: WORLD
90,414 Destiny 2
88,809 Wolcen: Lords of Mayhem
74,530 Ark: Survival Evolved
73,411 Team Fortress 2
I'm not sure if "current players" means people who just have the game currently installed or people who have the game installed AND are active/recent players of the game. Either way, the results are interesting to see.