It really depends on the game, but generally speaking, 20 year old games (that would be from 2005) work on modern Windows just fine. Games developed back in Win9x era are usually more troublesome.
I recently played Sinistar Unleashed on my Linux laptop.
I was never able to get this game working on regular Windows hardware, even when I bought the game brand new and tried running it on a contemporary computer, but it runs fine with Wine and Proton.
I decidedly could not get it working on a dual boot of Windows 10 (that I installed just to play to it).
Granted, even with Wine it wasn’t trivial to get working, but it wasn’t that bad. The game is actually not bad, I would have loved playing it as a kid, but I had to wait 25 years for Wine to let me play it, apparently.
I actually didn't for this, I was able to mount the ISO with linux and then run the executable directly to install it, then futz around with Wine settings on the install path to eventually get the game launching.
