While some of Microsoft's older game titles, such as Age of Empires II HD (a 2013 update of a 1999 game) are found on Valve's Steam platform, its latest high-profile titles, such as Forza 6 Apex and Quantum Break, are exclusive to the Windows Store. But this is going to change, with Microsoft planning to release more titles on the popular store.
Phil Spencer, head of the Xbox team at Microsoft, was talking on Giant Bomb's E3 stream, via GameSpot. When it comes to PC gaming, the Windows Store is very much an also-ran, with Steam the dominant force. As Spencer noted, "I don't think Valve's hurt by not having [Microsoft's] first-party games in their store right now. They're doing incredibly well." Accordingly, Spencer said that Microsoft "will ship games on Steam again."
Meanwhile, Microsoft's own experience had been more inconsistent. While some games have done well in the Windows Store, with Spencer naming both Forza 6 Apex and Killer Instinct as successful titles, he said that "Quantum Break wasn't our best PC release" and that Gears of War Ultimate Edition was merely "OK."