Huh. Didn't realize it started today. Will have to check my wishlist.

Anyway, recs in no particular order:

• Kena: Bridge of Spirits is a lovely little game. Some great East Asian influences, and a really great art style. Combat is sometimes surprisingly difficult. Some fun puzzles and platforming make up a lot of the game.
• Death and Taxes is a short and darkly humorous game where you take on the role of the Grim Reaper and decide who lives and who dies in a workplace-like fashion. If you're a fan of the web series, Purgatony, this might remind you of that. It's got a touch of satire to it as well, but not super pronounced. You'll find that mostly in the details and consequences of who you let live and who you let die (and there are consequences, some very significant).
• Heaven's Vault is a narrative game that takes place in space. Linguistics (or rather translating text) plays a role in the game and it's got a hand drawn, cel-shaded kind of art style.
• A Story About My Uncle is a first person, narrative driven, and entirely nonviolent game, with a bunch of cool swingy mechanics (so lots of gameplay, just not shooty bang stuff) and a fairly sweet story. You meet all sorts of fantastic, alien creatures on your adventure, platforming through a strange and beautiful world. Art direction is lovely, honestly.
• ABZÛ is just straight up awesome relaxation (with a few less relaxing points every so often) from some of the devs who brought you Journey and Flower. This time, it's all about diving and swimming through fascinating locations that vary from colorful reefs to areas reminiscent of long forgotten temple ruins (the name comes from the Sumerian and Akkadian word referring to underground aquifers that played an important part in some Babylonian mythology).
• Quantum Conundrum - Do you like Portal but wish it had a little John DeLancie commenting on your actions? Then this is for you! A fun puzzle game heavily inspired by Portal (the lead dev worked on the original Portal, if I recall). It's aimed at a slightly younger audience, but I think it works for everyone. Good vibes all around.
• Okay, not a hidden gem exactly, but if you like space, No Man's Sky isn't the disappointing game it was on release. I'd urge anyone who likes space and exploration to at least give it a shot. You can turn on creative mode and not worry about any survival elements as well. It's got a bit of a plot to get you used to the galaxy (and also explain some of the lore), but you can just do whatever you want and ignore that. Three alien races and you can learn words from their language by interacting with them or interacting with pillars on various planets that will teach you a word. I like this part of the game a lot for some reason. There's some other lore hidden around as well, but it's really up to you if you want to discover it or not.

Edit: I forgot about Blacktail. I haven't finished it yet, but it's a new take on the Baba Yaga myth and stars the voice actress who played Meg in Hades. That lovely, husky voice.

Edit 2: If you're looking for something a little old school, Jade Empire is a fantastic game by BioWare. KOTOR, but with real time combat that's heavily inspired by kung fu films and carries that general vibe with a bunch of East Asian visual aesthetics thrown in. If you like Crouching Tiger and similar movies, this is a great game to play, especially if you're also a fan of BioWare's RPGs (or just RPGs in general, honestly).

These next three are very hit or miss and some may find them either unpolished or just not that enjoyable. I'm listing them because they've got either an interesting story, or interesting mechanics. You'll notice the last two have a "mixed" rating, so this is more about "if you like the idea, maybe try it".

• The Vale: Shadow of the Crown is a narrative game that puts you in the shoes of a blind princess. It was made to be a game that blind people can enjoy, and the controls and mechanics are fairly basic (and it's keyboard only as far as I remember, but there might be controller support, I don't know), but the audio design is fantastic (for obvious reasons). There's some combat, and it's all about timing and listening for cues. I honestly think it's a fantastic game, but it's not for everyone. Good news is that it has a demo! Try it out first. Also, WEAR HEADPHONES. It's actually a necessity here. Binaural recording and object placement is entirely dependent on your ability to hear things (since you can't see anything, though it's got some pleasant screensaver-type visuals which do fit the theme of the area you're in).
• eXperience112 is a bit of a weird game. It's kind of a point and click adventure, but you don't control the main character. It takes place on an ocean vessel where something's gone wrong. You essentially play a camera operator and what seems to be the only survivor speaks to you directly so you can point her in the right direction. Also, she remembers when you last saved. If you don't play for a while, she'll comment on the fact that you left her alone for a while. It's buggy, but interesting.
• The Occupation is kind of the middle ground between a walking sim and immersive sim, which sounds like a weird description. It has narrative and some gameplay elements that you'd find in immersive sims (open-ish levels, multiple characters to speak to and ways to complete a level, some stealth, etc.), and every level takes place in real time, which is important because you'll have scheduled appointments for interviews and you'll be gathering evidence before that time is up, so you'll be looking at your in-game watch often. That watch is the reason I find it gets into walking sim territory, because you're kind of restricted by it and it sometimes makes things feel a little "on-rails". The whole thing takes place after some terrorist event killed someone close to the main character, set in a kind of dystopian London, but with a very '70s/'80s vibe in aesthetics. It has a demo, so try that first. If you don't like it at all, you won't like the game. If you find it intriguing, later levels get more intense, so you might be interested in buying the full game. If you like the demo, then yeah, maybe buy it. It's not too long to complete.

Most of the games I listed aren't too long or time-consuming. The only significant exceptions are Kena and No Man's Sky. The rest can be generally completed in a few hours or a couple of days. Kena isn't super long either, but it does require a bit more of a commitment than the others.

Edit 3: Add Jade Empire to the "not short/quick" games list. Definitely requires some time investment.