Grand Theft Auto V is, at this point, the highest selling non bundled game of all time, selling a staggering 45 million copies across PS3, PS4, Xbox 360, and Xbox One. With its PC release, it could have gone two ways- either everyone who was interested in playing it had, by this point, already played it via one of its previous releases. Or the PC market, starved from the game for nearly eighteen months, would gobble the game up when it finally launched.
The latter scenario turned out to be true- within 24 hours of the game launching, grand Theft Auto V had already hit a million copies sold on Steam. Notably, these sales are only for Steam- any sales made via other outlets such as Amazon or Green Man Gaming are not included in this tally, which comes from SteamSpy, the unofficial, but extremely accurate tracker of sales on Steam.
That is incredible performance, and should show Rockstar that there is a market for their games on PC as well. Hopefully, that means the platform is treated as less of an afterthought in the future.