Ah geez, I guess in vaguely ascending order:
Red Dead Redemption 2: Pretty flawed game mechanically for sure but it compensates for its, let's say less than smooth, movement and controls with what is probably the best plot Rockstar has ever written. Also, I really, really like westerns. GTA IV was still better but after V I really didn't expect Rockstar to make something remotely as good as this.
Watch_Dogs 2: Lotta people slept on this because of how slightly below mediocre the first game was but, like, this shit was good. It combines level design and a toolset that would be right at home in an Arkane game with a GTA style open world and complements it with a tone of light hearted techie utopism that feels like a refreshingly bright approach to a Cyberpunk setting. Writing and characters are very hit and miss but eh.
Undertale: it managed to make me laugh out loud multiple times, which is something I can say about very few games in general. Sure, I could also talk about how effectively employs meta commentary on the JRPG genre, how it manages to be emotional, often even corny, without feeling overly sappy or how likeable and memorable its characters are but for me it mostly stands out for how funny it is compared to almost any other game. I mean, just compare it to for what passes as humor in the Borderlands games.
Disco Elysium: I was never especially into isometric CRPGs, having grown up on consoles. I will say, though, Disco Elysium won me over quite effortlessly. A impeccably written murder mystery that feels somewhat like Hunter S. Thompson trying to write a Discworld City Watch novel. Disco Elysium is firing on all cylinders when it comes to worldbuilding, politics, humor and atmosphere. The brilliantly mournful soundtrack deserves some praise too when it comes to pulling me into the district of Martinaise.
Death Stranding: Free from the Metal Gear series that he obviously stopped giving a shit about a decade ago, Hideo Kojima finally got to pursue another passion project and mostly sticks it to the landing with something that's as mechanically innovative as its narratively ambitious. If you can't take it at its subverting the expected gameplay tropes of open world action games to make a point about pacifism and collaboration you don't deserve it at its expanding the visual and thematic language of post apocalyptic fiction to make sense of contemporary sociopolitical fears and anxieties.
Zelda Breath of the Wild: You know how every Zelda after Majoras Mask was more or less a reaction to the criticisms of the previous one? It stands to reason that the game after Skyward Sword, which had to be the worst 3D Zelda, would be one of the best, and it was. Breath of the Wild succeeded in crafting something that feels like a grand adventure, mostly on the virtue of its vast, detailled and extremely interactive world. Breath of the Wilds Hyrule is gamings most exciting adventure playground and I loved every minute I spent in it.
Bloodborne: From Soft was definitely one of the big innovators of the last generation, more or less creating a new genre from the ground up. If I went by gameplay alone, I'd say Sekiro was my favourite, but I wont, so it's Bloodborne. Bloodborne is an artistic marvel of horror both gothic and cosmic tied together by human intrigue. It fleshes out a very complicated world with minimal exposition and deserves a lot of credit for that.
Witcher 3: Like many a young adult in a state of advanced social alienation I like fantasy. Witcher 3 ist the best playable fantasy novel I ever had the pleasure to play. It delivers an extensive fantasy epic grounded by what is some rather excellent character writing.
Pathologic 2: The first Pathologic was a pretty messy affair all around, low budget, half finished and held together by duct tape and good will alone. It did, however, have writing beyond anything else you see in games. Pathologic 2 takes this writing and puts it into an actually competently made, and visually stunning, game that lives up to its kafkaesque ambitions. God, 2019 sure was a great year for games.
Final Fantasy 7Remake: You can now accuse me of only putting it this highly for being the most recent one I have played, and you probably wouldn't be wrong but it sure did leave a lasting impression on me. Now, I have never played the original FF7 and am only familiar with the broad strokes if its plot through osmosis alone but for adapting only a fraction of it, Remake already stands as an absolutely breathtaking adventure in its own right. The game frequently had me smiling from ear to ear with how disarmingly charming it was, whether it was an elaborate Moulin Rouge inspired musical sequence, picking flowers with the resident manic pixie dreamgirl or fighting through a mad scientists laboratory with Diego from Ice Age. FF7Re is a 40 hour tour de force of relentless charm and some of the most baroque spectacle I've ever seen in a game.