1. By a country mile, Witcher 3.
I have to think more about the others. It's hard. I have a lot of games that I appreciate as art (story + gameplay) but also games that I like for pure gameplay reasons. I don't naturally think of them in terms of rankings.
Red Orchestra 2/Rising Storm comes to mind in terms of gameplay, had the best time with the multiplayer. I used to play Counterstrike: Source a lot. Starcraft. Age of Empires II/III. I played a lot of the original Call of Duty back in the day (particularly multiplayer). I also played the original Half Life (plus expansion) a lot as a kid. Grand Theft Auto III and GTA Vice City. Jet Set Radio. Soul Calibur 2.
Story games: Bioshock-Bioshock Infinite, Witcher 1. RDR2, Fallout 3, Ghost of Tsushima
Dark Souls III, Bloodborne, Sekiro.
Metal Gear Solid series (1, 2, 3, 4)
Zelda Ocarina of Time, Star Fox 64. Resident Evil 2/3. Deus Ex Human Revolution