If you want no DRM, you are basically only going to get your games from GOG.

https://www.gog.com/en/games?tags=fps&features=coop&order=desc%3Abestselling&hideDLCs=true&releaseDateRange=2015%2C2025

Why emulate ? The Master Chief Collection is available on PC. It’s missing Halo 5 though. And then Infinite went ahead and cancelled this whole storyline.

The Sniper Elite series is basically nazi-killing porn. Those won’t let you down, especially if you enjoy unplanned testicular detonations happening to nazis of any kind.