Personally I would play the Marathon series of games. Love the narrative and atmosphere of those games.

edit to add a link for the lazy: https://en.wikipedia.org/wiki/Marathon_(video_game)

FYI: There's a modern source port for the Marathon series called Aleph One[1]. 60+ FPS support was recently added, so it's running better than ever.

[1] https://alephone.lhowon.org/

Just a smattering of shareware games that I played growing up that never got big enough to get modern ports. A more capable GPU could also be nice for having the emulator drive modern screen resolutions smoothly.