And certain types of games have a _ton_ of ancillary applications. For flight simulation, I rely on 2-3 additional contollers, some of which I am fairly certain either won't have driver support, or at the very least will have some major issues with the GUI and configuration.
Then, there are things like head tracking which are either another dedicated peripheral which may or may not get drivers, or a set of apps which feed from a webcam and output the signal to a standard driver that games know to check for.
Finally, most 3rd party add-ons have custom installers, and I'm guessing most of them won't have a working Linux version. So, while I'm sure it's possible to run, say, a vanilla X-Plane on a non-Windows installation with no peripherals/apps/add-ons, I just see a mountain of work to get a normal, heavily custom installation working.