Your most recently played title that ya consider an 'underrated gem'

ObsCure

Not exactly underated at 99% positive reviews but i'm gonna go for a game that I think should be more popular that it currently is.
Hexcells Infinite. Or any of the hexcells games really. They are just a perfect puzzle game. I think I know have more than 50 hours total on the 3 games combined!

The Journey Down is great, but then again I kinda expected that (I really wanted that game for quite a while now).
I could name a few games which I consider overlooked, but I'm too bust at the moment. :P

Out There Somewhere Enjoyed it, but it is very very short.

The Dark Eye: Memoria.
Sadly it needs Chains of Satinav to understand it, but it's IMO the second best Daedelic point 'n' click after Night of the Rabbit.

But my usual answers to this question are Remember Me (most of the game was left on the chopping pad, yet it is one of the best games of its kind, so it shows how insanely great it could have been) and Brink of Conciousness: Dorian Gray Syndrome.

Tiny and Big: Grandpa's Leftovers

I think people are discouraged from trying it because of the weird name, but it's a very fun game.

Heroes of Might and Magic IV

The only games i've played recently have been dark souls 1 & 2 and Demon's souls, I wouldn't consider then underrated in the slightest.

I've had my eye on White Night since before it was released, I'm planning on picking it up once it goes on sale especially since you recommend it.

Thanks for the With Night advice ! Seems an awsome game... Will give a go for sure ^^... In a way like "living in the shadows game", I'd say Echo of The Wilds . It's so atmospheric and visually impressive (pixel alert) .... Also, the gameplay is relaxing and immersive at the same time.
ヽ(◉◡◔)ﾉ

Went back to Alpha Protocol recently. I have no idea why it didn't get much critical acclaim.

Severance: Blade of Darkness, sadly removed from gog.com store because codemasters no longer hold rights to it.

PS.
Hope i beat it this time

I just finished Gods will be watching, and although it is not a hidden-gem as PC GAMER gave it an 81%, i nearly did not by it due to the only "slightly positive" reviews on steam.

The game puts your protagonist in 7 situations, that you have to survive by planning out your activities . The first mission for example is an hostage situation, where you are one of the captors and your boss is hacking a security system. You are tasked to keep the situation under control, in order to do so, you have to decide if you want to talk to the police to delay their intervention, calm the hostages or help with the hacking process and so on. As every action has negative consequences and some decissions have a chance to fail, its amazingly tense.

When the game came out it only had one difficulty setting, as the game design was intented to let you fail multiple times, before you finally succeded, but they added a patch with different settings so now everybody can enjoy it. I would still advise to play it at least on"Original Light". I think the high difficulty, which lets you become easily frustrated, lead to the many bad reviews. Additionally, some people are put off, as your decissions don't seem to matter in your playthrough, as for example, someone you had to sacrifice in a previous mission is alive again in the next episode, with nearly no explanation to that, but this is part of the story, and only some decissions really change your playthrough.

I highly recommend to check this game out!

http://store.steampowered.com/app/274290/

Well that was my "hidden" gem I played recently :)

El Shaddai Ascension of the metatron

https://www.youtube.com/watch?v=mIGaTCutqQ4

Unholy Heights for sure!

Also Witcher 1, I know it's not so underrated, but I consider it more of a cult game since a lot of people just play W2 or W3 straight away, but man W1 is awesome!

Survival: Postapocalypse Now, the russian DayZ that is actually less frustrating than DayZ! It's not better but definitely worth it's price.
And Blockstorm, that is sometimes given away by IndieGala. A very fun and blocky FPS.

Railroad tycoon 3. Many people say it wasn't as good as the second one, but I think it is as good, or better. It may not be as in-depth as the previous game, but it was still incredibly fun. For a game released 10 years ago, it still holds up pretty well in gameplay. The scenarios are actually incredibly challenging, and I struggled to complete them even on medium difficulty. Even though online multiplayer no longer works, I was still having RT3 LAN parties for a while.

Dead Space 2.

That's a joke but honestly, I've been playing pretty popular games lately. I guess I'd say Crayon Chronicles. It's pretty uh... Unique?

There is one good mod for Amnesia with the same name (White Night).

X-Com: Bureau Declassified, I liked it very much, too bad a bug prevented me to finish the game :P

store.steampowered.com/app/329320 QbQbQb its one of dozens of greenlit keys from various bundles i don't remember buying- but this was the only one i actually played and loved. in fact im going to play it right now (soon)

note: sorry i cant seem to figure out how to do hyperlinks here

Game of thrones RPG game was a pleasant suprise ;)

I'm not sure if it qualifies as an underrated gem but Brothers - A Tale of Two Sons didn't get nearly as much attention as it deserves.

Depth Hunter 2: Deep Dive
http://store.steampowered.com/app/248530/

just a nice relaxing diving game; has some "missions" mostly just swim around. Its great.

MIasmata - very unique, I finished it 4 times already, I wished it had more replayability, since steam sales are coming wait till it's -66 or -75%. :)