Asklemmy

Unreal Tournament, the one that was abandoned in favor of Fortnite (eugh). Like sure it would never be a big hit like Fortnite, Arena Shooters are out of fashion after all, but Epic didn't even give it a chance for starters, they basically just rushed it out the door with a skeleton crew, no budget whatsoever and were begging for community members to do free work on the game for them. In retrospect the game was doomed to fail from day one.

Desert Strike was so cool.

FreeSpace 1 and 2!

It's not really forgotten, but Wing Commander has been abandoned, and a proper modern rebuild of it would be fantastic.

Also, I want a new Deer Avenger.

Battle for Middle Earth. With the resurgence of RTS games lately, including many older ones getting remastered, I would absolutely love to see a proper remaster and release of BFME2. Unfortunately rights issues mean it's very unlikely to happen.

Battleborne - I found it enjoyable but because it was superficially similar to Overwatch it absolutely bombed.

I don't know if it's forgotten, but it's forgotten to me. There was this ant game where you had a colony of ants that would go collect food, or attack other colonies. There was this very pixelated top-down map view where you could see the brightly colored food disappear pixel by pixel as they ate.

I can't figure out what the game was but I loved it.

Mass Effect Andromeda, the middle of that game dragged, but the first third was pretty good and the last third was amazing, but most people didn't stick through the boring middle to get there. I really wish it got dlc and sequels, I wanted to see where that story went.

Definitely Icy Tower

Also, not really a video game, but those desktop destroyer type games. I'm not sure what any of them were called but it was a fun waste of time in my computer class.

Soul Reaver

My whole family loved these games.

Later, I realized Amy Hennig worked on these at Crystal Dynamics before leaving for Naughty Dog where she worked on the Uncharted Series.

If there is one game out there that I think deserves a second chance, it is definitely Alpha Protocol. This game came out in 2010 and was created by Obsidian Entertainment, the makers behind Fallout 3 and Fallout: New Vegas. This was the first-of-its-kind 'espionage RPG' with a truly, wholly unique dialogue system that has truly never been replicated since. Unlike mainstream RPGs of the time, you pick from several different 'tones' to speak in, in which gives the game hundreds of outcomes and dozens of endings. For example, according to Raycevick in a recent video, love interest can snipe you after a boss fight, poorly-treated damzels can attack you in the dead of night, contracts you're hired to kill can be baited into their demise through dialogue, and a whole host of other things.

The problem is that Alpha Protocol was lambasted by critics due to its incredibly buggy launch state and unpolished graphics. It never met the sales requirements that SEGA was expecting from it, and so, a few years ago, the game was pulled from all storefronts, never to be played again - until now. That's right. Thanks to the legends over at GOG for their incredible work, Alpha Protocol is back on sale, complete with achievements, localization, modern compatibility, and cloud saves. All without any form of DRM. But, the bugs in the game are still present to this day even in the GOG version, and so you might end up finding some humorous bugs and glitches.

Source: Making a Game Last Forever

Arcanum: Of Steamworks and Magick Obscura

An awesome RPG by Sierra (Fallout1+2). It was a bit unfinished, but you had such a great roleplay-experience. A second part was planned using Source-Engine.

Also:

FCK 
GNM

Operation Wolf.

Defender of the crown.

Gauntlet (and sequels).

The Settlers.

Syndicate.

Fury of the Furies.

Cooking Mama.

Tongue of the Fatman.

Turrican 1 and 2.

Zool.

Snow Bros. Nick and Tom.

Double Dragon.

Golden Axe.

Rick Dangerous.

Blake Stone.

Antix.

Screamer.

Soldat.

Speedball 2. Brutale Delux.

Lemmings.

Sid Myers Pirates!

Battle chess.

Shadow of the Beast.

Altered Beast.

Agony.

Strider (arcade)

Death Rally.

Stunt Car Racer (msdos)

Can add more soon

Age of empires 3. The civilizations are packed full of unique units, cards and mechanics compared to previous games. The card deck mechanics and treasures speed up the early game and allow for a lot more flexibility and adaptivess. The game looks beautiful the 2005 version kind of runs like shit but the definitive version has made a lot of balance and performance improvements.

Anddddd shooting formations of infantry with cannons is fun as.

Spore and Impossible Creatures

Kind of similar but these games are conceptually genius. How tightly Creativity and Strategic Interest are packed together is hardly seen ever again.

And animals are always a good idea. Even horrible games like Pokémon survive just because we like funny little friends.

MechCommander 1 and 2

F-ZERO. Truly a devastating loss. 99 is cool, but there's no guarantee we'll ever see a completely new title ever again. There was no other series with the same level of snappy controls, character design, music and challenge. It really is in a league of its own.

Star Wars: X-wing vs TIE Fighter

https://en.m.wikipedia.org/wiki/Star_Wars:_X-Wing_vs._TIE_Fighter

Destruction Derby 2 was loads of fun. I was going to say something like Choplifter, but I saw some video the other day that seems a perfect fit.

Not underrated, but I would love to have a next-gen SOCOM, and wouldn't say no to another Wipeout.

But hey, who doesnt need 43 new JRPGs?

Wildstar

The original Unreal. For me it was a perfect combination of beautiful graphics (back in the days of course) and a soundtrack which complemented and elevated the atmosphere of that game. And the gunplay was nice, with a collection of somewhat unconventional weapons. A relic from a time where developers were not afraid to experiment a bit.

Hunter: The Reckoning on the original Xbox.

Psi-ops. That game where you play a psychic special forces guy, fighting against other psychic special forces people, who were apparently your former coworkers or some shit. The ending was a setup for the sequel, but sequel never happened, now I will never know what the story was!

Alley Cat for sure

I enjoyed Rampart tremendously back in the day. It had a lot of ports, but I'm surprised it hasn't had any remakes or clones in the last 30 years.

Freelancer

Dark cloud 2

Zone of the Enders: The 2nd Runner

Blast Corp 64

Metal Arms: A Glitch in the System

Blur

Guild Wars 1

Not forgotten or obscure but... Assassin's creed 3. Yeah the main character sucks but I love the missions and map. Also has just the right amount of pirate like missions (in 4 is too much). I don't understand why people loved 4 so much the story of that game sucks lol and the villains are so forgettable.