Immersive Sims: Deus Ex; Vampire: The Masquerade: Bloodlines; S.T.A.L.K.E.R. Shadow of Chernobyl; Tron 2.0; System Shock 2. Absolutely essential games if you like "Shooters with powers" .
RTS: Age of Empires II Definitive Edition (out in 2 weeks). The Total War games. Warhammer 40k Dawn of War 1+2; Homeworld Remastered; Supreme Commander- Forged Alliance; the SpellForce series; (whenever it's released) WarCraft III Reforged; StarCraft 1+2 - this is just scratching the surface of the strategy game genre that has almost 40 years of history on PC, and most of those games are still playable, and many hold up. GOG is your gateway to strategy game history, and it is incredible. Steam's a better place for the more polished, AAA iterations, most notably the Total War series.
There are other genres, of course. Point'n'click adventures, 1st person puzzle games, real-time city-builder games, Paradox's grand strategy games, tons of 4X strategies, weird ambitious and janky RPGs that only ever get a PC release and then become cult hits;
PC Gaming is not, contrary to popular belief, "all about the flashy graphics" . It's a treasure trove of variety of genres, many of which have seen a recent resurgence, but also have established classics lovingly preserved via decades of back compatibility. There's always something new to discover, and the multitude of retailers like Fanatical, IndieGala, Humble Bundle, Green Man Gaming, Steam and GOG (to name just a few) shine near-daily spotlight on some more obscure games via sales, allowing you to try to find niche games in a genre that interests you.
