By number of copies sold or hours played even just those six are a huge chunk of "PC gaming". Including say the top 15 of the last 3 years, you can pretty much call all the rest of PC gaming a long tail roundoff error in terms of copies sold or hours played. It doen't really matter if for these 45 titles there are 4500 titles that work perfectly on Linux.

Depends how you look at it. If 95% of games play fine on Linux, and if a significant percentage of those play better on Linux than they do on Windows, then it's clearly not as far behind as you are trying to argue it is.

I think all it comes down to is: how bad is bad? To me, if 9/10 work equally well and 1/10 doesn't work at all, then that's way worse than unacceptable. I.e. not even close to acceptable.

Others might shrug and say "hey 9/10 that's great, and if 3 of those run even better then I love it!"

Yup. I'm in the latter group I suppose, since I don't really want to deal with any title that has intrusive DRM or anti-cheat as it is. I do security research and they don't tend to like some of the stuff I have on my system as it is.