Can't believe I just now saw the news that Horizon Zero Dawn has sold over 20 million copies! People naturally make some comparisons to the sales of The Legend of Zelda: Breath of the Wild since the games both belong to the same genre and were released at a similar point in time in early 2017. I would point out though that Breath of the Wild was the latest installment in a franchise that had been established for generations, while Horizon was a new IP at the time. But there's also another way in which Horizon's success stands out: it's now the top-selling video game ever to star a solo female protagonist. The previous record in this category was held by 2013's Tomb Raider reboot, which had sold 14.5 million copies as of last November.
I think the success of both games goes to show the difference that simply investing comparable resources into games about women and girls as one might sink into games about men and boys can make. Statistically-speaking, that ain't traditionally happened. Traditionally, games with a female-only protagonist had, on average, only 50% of the marketing budget of female-optional games, and 40% of the marketing budget of games with male-only protagonists.* When people can't see them because they're scarcely advertised or they look less impressive than other games, it's no wonder they don't typically sell as well.