Last game before the top 20!

#21 - A game Nintendo has released on many of their platforms over the years, but its best version is actually a PC port.

Prison Architect is correct, but Kingdoms and Castles is not. If I'm not mistaken, that game is still just on my Wishlist, haven't played it yet.

Prison Architect is quite fun, I played that a fair bit as well. Kingdoms and Castles I actually also never actually played, though I had been eying it several times. It’s still on my wishlist as well. Now though I’ve seen that the developer of that is coming with a similar Roman city builder, which looks pretty good. I might get that one.

#39 - Stealth, Sniping or big guns, whatever approach floats your boat in this game is possible.

1. When it came out, the game was absolutely lauded for it's story and storytelling, and it's only real gripe among reviewers was that the graphics were a bit outdated.
2. It's a bit of a meme that people hearing about this game again makes them immediately re-install it on their PC.
3. The game got released just 2 days before Diablo 2 and 3 weeks before entry #37 - at least in the US. In Europe #37 released the same day as Diablo 2
4. It's the first one of a series of cyberpunk games, with much of the story being about conspiracy theories being true in that universe.

#38 - Thwart an Alien Invasion with a team of soldiers and some researchers trying to reverse-engineer the alien tech into something useable by humans.

1. You start in the late 1970's and with according tech and weaponry, just somewhat adapted for your specific needs. Later on, you'll research laser weaponry, plasma rifles and coilguns, but psionics won't do anything.
2. Your alien foes are made of Sebillians (a race of fasr-healing and very strong but short-sighted lizardmen), Caesan (basically the Greys, good sight but mediocre health), Reapers (turns your soldier into a zombie if he hits you in melee), Androns (robotic infantrymen with a total disregard for cover), Drones, and the Praetor who are leading the invasion. 
3. It got rereleased a year after it's release as the "Community Edition" with some community-suggested rebalancing and mod support.
4. As the Alien Invasion already alludes, it's like X-Com, but it's not an X-Com title.

#37 - "It is a world, of darkness"

1. The quest of this RPG plays over a timeframe of about thousand years, which is foreshadowed in a discussion early within the game.
2. As the thousand years alluded above suggest, you're playing a Vampire, but he's not yet one of them at the beginning of the game.
3. It's the first videogame that came out based on Vampire: The Masquerade.

#36 - This series is one of the most-cited successors to the classic DOS game Master of Magic.

1. The first game of the series was totally broken and got 6 patches within the first two days, but the core mechanics were not really good, so it got a successor that entirely replaced the first game, which itself got an expansion that replaced the previous replacement. We're talking about the last one in the line.
2. You play as the sovereign of one of the 10 nations, split between the good Kingdom faction and the fallen Empire faction.
3. If you play through the story, then you find out it's actually a stealth prequel to another 4X IP from the same developer and publisher, which itself is THE most-cited successor to Master of Orion.

#35 - You lead the development of new video games for a console manufacturer

1. The game only came out in Japan as it released just days before the console stopped being produced
2. At the end of the game, the Adventure-RPG suddenly turns into a Shoot'em up.

#33 - One of the most hailed tactical RPGs on PC - if not THE most one.

1. "Elliot, you Idiot!" *slap* *slap*

#32 - A medieval Fantasy city/city state builder.

1. This game is still in early access on Steam, though it's practically finished. It features counterparts to several of the usual fantasy races, though with some interesting twists and quirks.

#28 - "Game Over, Yeah!"

1. By today's standards, this racing game is very short and simplistic, but was pretty much revolutionary back then.

#27 - Heroes lead armies in turn-based combats over a large world map to dominate their opponents and conquer their cities.

1. Uniquely to this entry in the series, the Heroes don't just stand around and provide stat boosts and the occasional spell support to the troops, but can actively fight in the battles. In fact, you can have more than just one in each of your armies.

#26 - The goal of this game is to colonize Mars and make it habitable to humans without protective gear or oxygen masks.

1. You play as an AI, and what decisions that AI takes in discussions with researchers and colonists will develop your personality, rationale and how the game can progress in some ways.

One game left.

#20 Uncharted 4: A Thief's End

• In the final part of this game the player controls the main character's child

#19 Nier: Automata

• Machines are replicating old human concepts and societies in a post-apocalyptic earth

#18 Final Fantasy VII

• Among the notable themes in this very political JRPG are environmentalism, impact of corporations and industry on nature, life and birth, and economic disparity in society

#17

• Life ended nearly a thousand years ago, yet here you still are
• A military machine swarm went rogue and decimated earth's biosphere

#16 Final Fantasy VI

• The main villain went insane due to cruel experiments that gave him great power

#22

Change YoY: =   My Rating: 9.3 / 10

I've long since lost track of all the Metroidvania games I've played over the years, from the two series that gave the genre its name, to far too many indie games to even count at this point. That effectively spans a period of 30 years if we consider Super Metroid as the origin point, and out of all of them, Hollow Knight stands as the unquestionable peak of the whole genre in my opinion. Not only is the game instantly visually gorgeous, it also has some of the tightest, most rewarding gameplay that I've experienced in any 2D Metroidvania. In addition, the setting is wonderfully designed, each location flowing into each other in a way that always makes sense once you realize where you are, making each location in the world feel like a place with a past and a culture of its own.

The game also lets the player figure out a lot of the story for themselves, rather than spelling everything out, which is one of the elements where the game's Dark Souls inspiration shows up. The characters talk about past events and many items you find provide hints at the larger context that everything fits into, but much of it is still left for the player to put together as they discover new locations and characters that each provide another piece to the puzzle. Very few games have held my interest as effortlessly as Hollow Knight, even through the most challenging sections and battles, I never felt the need to stop playing for long. It effectively strikes a perfect balance between challenge and constant sense of discovery. There are so many places to visit and secrets to find behind every corner that it's very easy to fall into the "just one more attempt" flow. The soundtrack is also one of the best of the last decade.

Finally time for the next batch of write ups. I guess all I'll add is here are the top 15 games of my teens:

Seems to be too difficult for you guys, even though some are pretty well-known titles 

#39 - Stealth, Sniping or big guns, whatever approach floats your boat in this game is possible. Deus Ex, found out by @Darashiva 

1. When it came out, the game was absolutely lauded for it's story and storytelling, and it's only real gripe among reviewers was that the graphics were a bit outdated.
2. It's a bit of a meme that people hearing about this game again makes them immediately re-install it on their PC.
3. The game got released just 2 days before Diablo 2 and 3 weeks before entry #37 - at least in the US. In Europe #37 released the same day as Diablo 2
4. It's the first one of a series of cyberpunk games, with much of the story being about conspiracy theories being true in that universe.
5. The main character is named J.C. and he's part of a police force, and while the game is the first that came out in the series, it's actually one of the last in the timeline, taking place in 2052 (though only one of the sequels confirms the date). Interestingly, the World Trade Center twin towers are missing in the New York skyline despite the game coming out before 9/11.

#38 - Thwart an Alien Invasion with a team of soldiers and some researchers trying to reverse-engineer the alien tech into something useable by humans.

1. You start in the late 1970's and with according tech and weaponry, just somewhat adapted for your specific needs. Later on, you'll research laser weaponry, plasma rifles and coilguns, but psionics won't do anything.
2. Your alien foes are made of Sebillians (a race of fasr-healing and very strong but short-sighted lizardmen), Caesan (basically the Greys, good sight but mediocre health), Reapers (turns your soldier into a zombie if he hits you in melee), Androns (robotic infantrymen with a total disregard for cover), Drones, and the Praetor who are leading the invasion. 
3. It got rereleased a year after it's release as the "Community Edition" with some community-suggested rebalancing and mod support.
4. As the Alien Invasion already alludes, it's like X-Com, but it's not an X-Com title.
5. The soldiers wear blue uniforms at first, making them wonder why they don't wear any camo (according to the description, it's due to the aliens seeing on a different color spectrum as humans do, camo doesn't influence their sights at all)

#37 - "It is a world, of darkness"

1. The quest of this RPG plays over a timeframe of about thousand years, which is foreshadowed in a discussion early within the game.
2. As the thousand years alluded above suggest, you're playing a Vampire, but he's not yet one of them at the beginning of the game.
3. It's the first videogame that came out based on Vampire: The Masquerade.
4. the mediaeval part plays in Prague and Vienna and the modern part plays in London and New York

#36 - This series is one of the most-cited successors to the classic DOS game Master of Magic.

1. The first game of the series was totally broken and got 6 patches within the first two days, but the core mechanics were not really good, so it got a successor that entirely replaced the first game, which itself got an expansion that replaced the previous replacement. We're talking about the last one in the line.
2. You play as the sovereign of one of the 10 nations, split between the good Kingdom faction and the fallen Empire faction.
3. If you play through the story, then you find out it's actually a stealth prequel to another 4X IP from the same developer and publisher, which itself is THE most-cited successor to Master of Orion.
4. You can design all troops yourself, provided you have researched the equipment that they would then wear, though there is an option to automatically upgrade the design with newly researched armor and weapons. 

#35 - You lead the development of new video games for a console manufacturer

1. The game only came out in Japan as it released just days before the console stopped being produced
2. At the end of the game, the Adventure-RPG suddenly turns into a Shoot'em up.
3. The came is packed with charactera and cameos from the video game company that produced the game, punny recreations of games from other companies and if they couldn't get around them legally, pixelated the references.

#33 - One of the most hailed tactical RPGs on PC - if not THE most one.

1. "Elliot, you Idiot!" *slap* *slap*
2. You can hire your mercs from two sources, the second one run by guys from it's predecessor.

#32 - A medieval Fantasy city/city state builder.

1. This game is still in early access on Steam, though it's practically finished. It features counterparts to several of the usual fantasy races, though with some interesting twists and quirks.
2. Speaking about those races, the orc counterpart is a race of peaceful vegetarians, the elven counterpart  bloodthirsty tree huggers and cannibals, humans are very intelligent but prone to crimes, dwarfs cannot be born as they exist since forever, death-worshipping insectoids, and so on

#28 - "Game Over, Yeah!" Sega Rally Championship, found out by @Darashiva 

1. By today's standards, this racing game is very short and simplistic, but was pretty much revolutionary back then.
2. The game came first out in the arcades, but we're talking about the Sega Saturn port.

#27 - Heroes lead armies in turn-based combats over a large world map to dominate their opponents and conquer their cities. Heroes of Might & Magic IV, found out by @Darashiva 

1. Uniquely to this entry in the series, the Heroes don't just stand around and provide stat boosts and the occasional spell support to the troops, but can actively fight in the battles. In fact, you can have more than just one in each of your armies.
2. In the predecessor, there were 8 (or 9 with an expansion) different towns. In this one, there are only 6: Life, Death, Nature, Chaos, Order and Might. 

#26 - The goal of this game is to colonize Mars and make it habitable to humans without protective gear or oxygen masks.

1. You play as an AI, and what decisions that AI takes in discussions with researchers and colonists will develop your personality, rationale and how the game can progress in some ways.
2. The game starts as a peaceful base-building game, but after a while you get attacked and must then also build some defenses

#25 - An early 90's PC adventure game where the number of a specific letter in the title tells you how many characters you're manoeuvring through the scenario.

#24 - A God game that released (or rather came out of early access) this year.

#23 - A long time ago in a galaxy far far away *Cue synopsis text crawl with theme music*

#39: Deus Ex

#28: Sega Rally Championship, I think

#27: Heroes of Might and Magic IV? I think III had nine factions, so that makes me think this has to be four, though I haven't actually played it myself.

Another clue then.

#20 Uncharted 4: A Thief's End

• In the final part of this game the player controls the main character's child

#19 Nier: Automata

• Machines are replicating old human concepts and societies in a post-apocalyptic earth

#18 Final Fantasy VII

• Among the notable themes in this very political JRPG are environmentalism, impact of corporations and industry on nature, life and birth, and economic disparity in society

#17

• Life ended nearly a thousand years ago, yet here you still are
• A military machine swarm went rogue and decimated earth's biosphere
• Earth was eventually repopulated using advanced AI that would be able to continue working even after humans went extinct

#16 Final Fantasy VI

• The main villain went insane due to cruel experiments that gave him great power