It's definitely aged, but Lionhead (people who made Fable) made a weird game called Black & White, and it's a society building God sim, you are the hand of God, you can do good or evil, raise an animal minion to do your bidding. You can shower your people with food and gifts, or rain fireballs down when they anger you. It's a wild concept that's still pretty unique.
Command and Conquer and basically anything Bench suggested i've played and loved. Dark Souls is about the most challenging series out there, so avoid if you don't want to die 500 times lol. They are amazing games if you can trudge through. The Bioshock trilogy might be my favorite series ever. Mass Effect is brilliant also, although Andromeda, the final unrelated entry can probably be skipped.
Red Dead Redemption is a great rec, they had a DLC called Undead Nightmare and it turned the world into zombies and it's fantastic.
FPS, maybe check out Far Cry 3, The Master Chief Collection, or the Portal games. I like the rogue-lite ones like Immortal Redneck and Ziggarut, they are indies and cheap.
XCOM is cool, so is Wasteland for more of a turn based RPG game. South Park Stick of Truth was surprisingly excellent also.
Just because I love the genre, Binding of Issac, Enter the Gungeon, Dead Cells, Hades are all good time burners.