According to Wiki, the most played games are as follows.

Pay to Play Free to Play
PlayerUnknown's Battlegrounds (PUBG) CrossFire
Minecraft Dungeon Fire Online
Among Us Pac-Man Doodle
Tetris QQ Speed
RuneScape (subscription) Candy Crush
Microsoft Solitare

Here were what the numbers looked like in 2015:

most-played-pc-games

Here is a video of the most popular games from 2004-2020.