Neither of mine are necessarily "hidden gems" since they're reasonably well known in their respective niche genres, but are not exactly well known outside them, so I still think they're worth highlighting:

Caves of Qud, Overwhelmingly Positive (8,322 reviews), -15% CDN$ 33.14

This is easily the best Rogue/Nethack inspired RPG I have ever played. I say "inspired" rather than "-like" because this is more true to the originators of the genre than most games that get labeled with "-like" these days, especially in terms of its core gameplay and graphics, but just with some extra retro RPG elements added to it as well. Think Rogue/Nethack meets Zelda meets Final Fantasy meets Tales of Maj'Eyal but wrapped in a 70's style retro-futurism, post-apocalyptic, psychedelic scifi shell, and you won't be too far off the mark. The 1.0 release also just came out too which significantly improved the UI, and added even more QoL stuff, so it's a perfect time for new people to give it a try.

Citizen Sleeper, Very Positive (5,505 reviews), -70% CDN$ 7.79

From a previous comment of mine:

Citizen Sleeper is the best game I've played in quite a long while, and I highly highly recommend it if you like Time/Resource Management and Interactive Fiction games... Although it's somewhat light on the management aspect, it's not super challenging, and it's mostly an IF game. Similar to Disco Elysium, the writing is absolutely top-notch in it, and it manages to get you to fall in love with the characters in a short amount of time. The only disappointing thing about it is its length. After 16 hours of play I felt pretty much done with it despite not having found absolutely all of the endings yet (only got 22/27 achievements). So I'm really hoping that Citizen Sleeper 2, which is due out in 2025, will be much much longer.

(review from my younger teen, since they play a lot more games than I do these days)

Mages of Mystralia - Very Positive (815 reviews) - action adventure, very pretty, fun, but can be difficult. Has a good story with interesting plot twist

Critter Cafe - Mostly Positive (65) - cute critters, puzzles really hard, cafe management kinda stresful, but the cafe game actually pretty fun and you get to decorate things! Also, cute critters.

overlooked "grads":

Apico - just over 1000 reviews. It's got cute bees, and fun characters. These guys also made:

Snacktorio - not officially released yet, but combine your love of cute things, cooking, and factory simulation obsession. Anticipating this, free demo available.

Ooblets -- Mostly Positive (1164) -- okay this one is mine. This is my favourite Pokemon title, even though it isn't a Pokemon title. They released last year and still "only" have 1164 mostly positive reviews? :( Maybe because they sold more copies on Switch, hopefully. You collect cute buddies, they follow you around town, and they dance (turn based card) battle! The NPC characters are interesting and erh, "neurodiverse" in unique ways. The whole place is great and cozy and cute and fun. Hard recommend. I already mentioned I don't play many games these days but I was so glad to have played this one to nearly 100% completion. I think I'll sit down with this one over winter break and play it over again.

I posted a nice list for the Summer sale, and going over things to update this time, it's pretty similar right down to the review counts (... depressing), so I'm just going to focus on one new game that's limping along at 23 rather unappreciative reviews:

Combat Complex -- 30% off: $13.99 (early access)

Twin-stick shooter against various bugs and robots with some basic ARPG gearing/upgrades but a more arcade feel, offering fantastically tight action with probably three key factors:

• Enemies target you but hit each other, so you manage their attacks to help your fighting instead of just staying out of trouble.
• "Frenzy" orb pickups, which act a bit like combo meter fuel except instead of chaining hits for combo, you make frequent choices about whether an orb drop is worth chasing, keeping you close to danger.
• Instant gun switching with overheating instead of reloading, so you fight hard and switch constantly between your three guns (and moments of not shooting for faster movement) to keep any one from overheating while getting the best out of their specific properties.

I play a lot of twin-stick and top-down shooters, and this does a great job mixing the arcade twin-stick feel of high-intensity swarm chewing with tactical top-down dungeon crawling elements, and it's just really special feeling to play, at least if you pay attention. Plus, it's extraction style instead of being a roguelite or static arcade run, so you're always right at the best action while still getting procedural levels to change things up. That said, there's no scoring and a lot of rudimentary parts, so it lives entirely on action quality and the fun of the fight.

Games like this tend to get really underappreciated, and I'd really like this gem to find its players, because it just makes me happy someone is out there making something like this (and I want them to feel encouraged by some $$ interest, dontcha know--my partner and I already bought ours). It's got a demo, so give it a chance to grow on you once it gets past the gentle introduction.

If you don't like words, here's a video (link-only, not a channel) of one mission a few floors past the demo (blame Steam's game recording for creating glitchy sound artifacts that weren't there in play): https://www.youtube.com/watch?v=oa8_m6QuvOg

I recently finished Afterplace which before my review was still Under the Radar.

It's a simple top down ARPG with a focus on story, characters and exploring a surreal world. While there's only a handful of upgrades and items the humorous writing and atmosphere made it a really enjoyable experience.

Underrated Great: Logistical, Very Positive (218 Reviews)

This game is a sort of puzzle, logistical, supply chain building game. Simple game play of drag trucks with goods from one place to another to complete the demands of a town, produce goods, or to upgrade industries. There are a bunch of modules, which are separate standalone maps. The dev has also created a Logistical 2, and 3, which are iterations on this formula and improvements on the engine/add new features. I have a few modules and would like to pick up more eventually.

This series culminated in the Buried Treasure Logistical 3: Earth, Very Positive (139 Reviews). Hundreds to thousands of hours of content in that one game. I plan to pick this up one day.

This series for me scratches an itch, and I can lose a good chunk of time playing if I'm able to sit down and play. Lately it has been a podcast listening game when I can sit down for a bit and don't want to think too hard.

I wanted to contribute but am on mobile and have little time to properly link and describe. Still I thought it would be a shame if I didn't bring awareness to these gems. I'll try and return soon to edit in more detail.

As my Steam account is approaching 1600 titles this was too grand a feat to parse thru it's entirety, these titles represent standouts I've enjoyed within the last year with fewer than 1000 reviews.

Proverbs - puzzle cross between Sudoku and Minesweeper
Hadley's Run - twin stick roguelike
Keep Keepers - co-op automation and tower defense, feels like a mix of Plate-Up and No Heroes Here
No Heroes Here - co-op defense
Wild Woods - co-op action roguelike similar to Unrailed with defensive combat
Brok - Funny detective Point-and-Click
Riftbound - best lane defense since Plants vs Zombies
Touch Type Tale - Great typing RTS fusion
Pyrene - card turn-based combat
Tipston Salvage - amazing co-op action driving forklifts
Arco - Turn-based RPG with good story
Feed the Deep - Roguelike Domekeeper
Depths of Sanity - Submarine metroivania
Offroad Mania - vroom

Honourable Mention (more than 1000 reviews):
Minishoot Adventures - so good, one of the relatively few games I've beaten

Any interesting visual novel?

Buried treasure : TETRACHROMA (108 reviews).

It's one of the most interesting Tetris-like release in the last few years, and that's coming from a Tetris the Grand Master player.

So it's Tetris with a gimmick, and the gimmick is very simple (as it should be) : each pieces have a color and you can only clear a line if the whole line have the same color. Each piece you place change color of the adjacent pieces in a line (think Reversi).

It's an elegant addition and really messes with your brain (in a good way).