Windows

I love Linux, and the sooner I can fully switch to it, the better. Having said that, you can't just pretend it doesn't have issues, that's a disservice to Linux as a platform, as it'll just mean that potential switchers will end up disappointed when it isn't issue free, and the things that they're used to working out of the box, don't in Linux.

Even outside the very real issue of software support, it isn't even 100% there for gaming yet:

1. Games still come out with, or get updated to have, anti-cheat systems that don't work on Linux. You might say that you don't want such invasive systems on your computer, but many others enjoy the games that employ such systems.
2. Features like HDR are still in the very early stages, requiring more setup than it would on Windows, and still being hit & miss.
3. VR? Even worse. People, including myself, have been utterly spoiled by Virtual Desktop.
4. Other advanced graphics features like DSR are missing, or require the use of unfamiliar third-party apps, that probably don't have the same level of accessibility as, for example, Nvidia's apps.
5. While most games should work out of the box, there are plenty that don't, and while it may be possible to get them to work if you have the know-how, that's a requirement that not everyone can meet.
6. I hope you don't like modding your games, because it's a pain in the arse on Linux. Most mod managers don't work natively, and while there are solutions to make them work on Linux via Wine, it's janky at best. Even some mods don't work, as they require features specific to Windows. Thankfully, the Nexus team is working on a cross-platform mod manager that should make it a whole lot easier, but until then you're stuck to no mods, painful manual modding, or janky mod manager solutions.