I'm loving Elite Dangerous right now. If you want something shorter, I'd recommend Her Story. If you want something extremely fun, I'd recommend Uplink. If you want a good adventure game with great humour I'd advice Psychonauts.
Those are my favourite games of all time, but there's also games like Papers, Please, Portal 1&2, TES Oblivion and Skyrim, Prison Architect, all Paradox Interactive Grand Strategy games (EU4, CK2, Stelaris are my favourites), Civ 5&6, FTL: Faster Than Light, Banished, Assassin's Creed 1, 2, Brotherhood and 4 (all the others are shit), Undertale, Middle Earth: Shadow of Mordor, KOTOR 1&
2, Stardew Valley, Planet Coaster, Beginner's Guide, Stanley's Parable and a friend of mine is absolutely in love with Dragon's Dogma.
Hoped that helped, it's quite a long list