How many years exactly? That might help suggestions, since a lot of things were released in every genre in the last decade or so.

In no particular order, a mix of genres:

• Valheim (small sale on steam too right now)
• Dying Light (FPS zombie game, action packed and very well done; the second game should come out end of year)
• Control (dat RTX and psychedelic effects; gameplay is ok and story is convoluted but a fun ride overall)
  
• Death Stranding (if you are ok with Kojima things and unique experiences)
• Frostpunk (steampunk city-builder survival)
• Rocket League (stupid fun and surprisingly reactive on GFN)
  
• Sleeping Dogs Definitive Edition (shorter GTA, Hong-Kong style, polished)
• Slay the Spire (the new OG in deck-builder games, "I'll just play a little bit more" for 5 hours)
  
• Monster Train (deck builder with enormous replayability and lots of fun, different from StS above but just as interesting in its own way)
• The Forest / Green Hell (for survival FPS)
  
• Firewatch (short first-person game, a small story with a somewhat open interpretation)
• Descenders (mountain biking fun)
  
• Age of Wonders: Planetfall (if you like 4X games and XCOM)
  
• Supraland (puzzle-action, toy-story inspired)
  
• Guilty Gear Strive (fighting game, pretty expensive right now though)
• theHunter: call of the wild (realistic walking hunting simulator, extremely well done even for people like me who don't actually like hunting and end up wandering around more often than not)
  
• Witcher 3 (even without knowing the previous 2, just look up a recap and dive into it)
• Kingdom Come: Deliverance (FPS where you start as an actual middle-age peasant, go through intense stuff and work your way up; a bit messy, very frustrating, very complex at times, yet amazing for those who go beyond that - which isn't everyone at all)
• Papers, Please (small "simple" yet polished indie game where you're basically a soviet border control officer)
  
• Ark & Rust & Hunt:Showdown for FPS/survival/having-no-life-ever-again
  
• Disco Elysium (isometric character-driver game with some randomness and having to replay loops until you advance the story, well-written and complex, got many prizes last year IIRC)
  
• Ghostrunner (it's like Celeste or Super Meat Boy but in 3D and cyberpunk aesthetic, you better have very low latency to play that though)
  
• Hollow Knight (acclaimed metroidvania 2d game with lots of polish, didn't hit the spot for me but it's extremely well liked for its quality and depth)
  
• Into the Breach (acclaimed turn-based strategy, same)
  

Note: if you plan on playing exclusively on GFN always check the game using the search bar before buying them on a given platform because sometimes GFN only has compatibility with one platform or the other (either Steam, Epic games store, GOG..)
Note 2: if you have the GamePass many of these games can be on it for free rather than on PC, also worth keeping in mind (not my case but something I've observed over time)