Sold over 100m units as a franchise, but a not as an individual game.
Wiki is not necessarily the best source, but here are the numbers:
World of Warcraft is third on PC games with 14.5 M, behind Overwatch at 15M, and Minecraft at 24M.
https://en.wikipedia.org/wiki/List_o...video_games#PC
It seems like GTA 5 is the best selling video game of all time.