I was almost not going to respond with Outer Wilds, since it feels like I played forever ago. But apparently I only played it in June of this year, so that's my choice. It's one of my favorite games now, if not my favorite game ever.
It's so good, in fact, that it's helping me get over this weird anxiety I have of talking about my hobbies with other people (including my closest friends). Outer Wilds is so good that even though I hate talking about games I like, I still feel the need to recommend it to people. And now that the floodgates are open I feel a bit more comfortable talking about my other favorite games, like Baba is You, which I got another person to play as well, and The Messenger, which I'm playing now and loving it.
Outer Wilds is one of those games that is better the less you know about it. So I will be a bit vague, bit this would be my pitch:
It's a space archeology game with a very good story, charming characters, and an intriguing mystery. It has fun mechanics, as I enjoy simply flying around in the ship (once I got the hang of it) and some unique puzzle design.
After the tutorial section it is an extremely non-linear experience.
Highly recommend, don't look up any spoilers though!
Unfortunately, I agree with the other commenter. It's very hard to talk about the game without taking a bit out of the experience.
I will say that it's a space exploration game, where you fly around a tiny (handcrafted!) solar system and explore the various planets. There are a handful of mysteries around this solar system and you eventually figure out how the various clues intersect.
It's also very much a game about information. You never gain upgrades or stats or anything, your character when you start the game is exactly the same as when you finish it. But you learn things about the solar system and your knowledge of this world and it's mysteries increases, directing you on where to go next and what to do. The game also doesn't present you with explicit goals, so at the beginning you can do pretty much everything you want, but there is an ending you will eventually reach by following the clues laid out around the universe (and I seriously recommend that you don't stop before the ending).
It's also a very hard game to replay, as after you know the answer to the mysteries, there's a part of the appeal that is lost. I wish I could forget about it so I could replay it fresh!
If you liked outer wilds I would check out Forgotten City. I just started it, but it has a similar feel. It's more piecing things together through dialouge rather than exploration but has a similar "the whole world is a puzzle" vibe with the a kinda rouge lite experience of needing to use what you learn each cycle to progress further.