Valve in their review Steam Year in Review 2021 published a lot of interesting information, including controller usage statistics. According to Valve, there are currently 48 million controllers and they are used in 10% of gaming sessions.
Back in February, the Steamworks update added a new controller usage statistics page, where developers can see detailed information about what kinds of controllers players use and how often. The data includes gamepads, joysticks, racing pedals, and even dance mats. In principle, anything that connects to a computer and can be used to play (like a banana) but is not a mouse and keyboard is considered a controller.
It came as no surprise to read that in 2021, over 70% of fighting and sports games were played with a controller, while for RTS games this number has fallen to less than 1%. Only 7-8% of gamers use a controller in first person shooters. In third-person action/adventure games like Elden Ring, the ratio between controller usage and keyboard/mouse usage is almost 50/50.
It seems that many PC gamers prefer to use the keyboard and mouse even in those games where controllers are in the first place.