It’s better today than it was a year ago, and WAY better than it was 3 years ago, and is still improving. There are a few categories of games where you are likely to have problems though.
competitive multiplayer games [kernel level anticheat, that one will probably remain a problem]
very old games [getting better all the time, because wine is getting better all the times]
very new AAA games [they mostly use one of a handful of game engines, so they tend to get fixed in batches]
I would say whether linux is ready for (windows) gaming depends on is different per person predicated on:
What categories of games you play
Any specific problematic game that is a dealbreaker for you
For me, I tend to play some older games, and there are a few that don’t work well. I don’t want to boot windows, so I just decide I can wait for it to get there for them.
For some people, “ready” means will run every windows program as if running on windows. We’re still a ways off from that, if we ever get there (it’s a moving target, as windows is still being developed…)