Celeste
I finally got round to playing (and beating) Celeste after having not given it the attention that it deserves for roughly a year. Now that I have, I'm incredibly glad I did so - this game is engaging, challenging and gorgeous. The gameplay is great, a solid and polished platformer with some interesting mechanics, but what really shines is the story. I can't remember the last time I was so emotionally involved in a single player experience like this - Celeste hit worryingly close to him and I was moved to tears on multiple occasions.
I was aware beforehand that the themes in the game were mental health-ish, but when I began playing and realised that my objective was not only to climb Celeste Mountain but was also to overcome the protagonist's anxieties and self doubt, it quickly became analagous to my own life. After only playing for an hour or so, I knew I was going to have to complete the entire game, no matter how long it took - not overcoming Madeline's internal demons felt like it would be losing to my own.
A truly remarkable game, thoroughly worthy of the deluge of praise it has experienced since its inception, and birthed from a game jam no less! Now to get all the collectibles...