The Sonic Racing games are the best counterpart to Mario Kart available on PC. Sonic Racing Transformed is the best of the 3 games (and bundles the very first game) but sometimes gets confused when switching up controllers, so you must delete the config file, so maybe because of that not the best introduction to PC. Team Sonic Racing is a bit less good but that input bug is gone.

Dead Cells

CARRION

Left 4 Dead 2

Hades

Try Rise of the Triad, One Must Fall 2097, and Goat Simulator

Game bundles like from Fanatical are a good start. You can't return them if you have issues, but they're great if you haven't played any of the offerings given.

A similar thing would be Xbox Game Pass, but that very much locks you into their ecosystem, and they're clearly done investing into worthwhile games.

SuperHot

The DOOMs

I thought the old homeworld games were great. Kind of RTS in space ships. They're old now but still good.

Tormented Souls was really good

Might consider getting something that only plays well on keyboard/mouse. Factorio comes up off the top of my head. Shooters also generally translate poorly to controllers, so perhaps that?

Total war: Warhammer 3? Baldurs Gate 3? Maybe those are available on console as well..