Yep, this games may be too modern for someone's taste, and some of them were talked about some time ago, but now they are nowhere it seems.
Alpha Protocol. One of the games you can not buy now, but can obtain by other means. It is spy game with bunch of shooting, story where your choices matter and...it really have this Deus Ex vibes, but is done more interesting than later Deus Ex games. And it really feels like bosses in this game are either superhuman or augmented. But your agent is also not a simple man, cause you have bunch of abilities you can gain (half of them are useless tho). Shoot terrorist, shoot mobsters and solve international conspiracy.
Cross Code. Pretty fun game about "MMO" game inside game, but with no actual MMO, fun and fast combat, great puzzle solving mechanics, interesting story with unexpected turns, good music, anime-like pixel graphics that fits it and some really hard bosses. Can't say much more, just love this game and wish more people be aware about it's existence. And it have free Demo on Steam.
Disaster Report 4: Summer Memories. Well, actually can recommend whole series, but first 3 games are on consoles and one of them does not even have English translation. But they are really rare games about surviving catastrophe, that is active exactly when you play. Everything is coming apart around you, city ruins, people dies, and you barely survive it yourself. For some reason this game have conspiracy in it, but I played it for environment and environmental destruction, and "oh shit, oh crap, what to do...oh, I am dead, reloading..." factor. Also this games are about Japan, so if you interested to know how it looks from inside, you can play at least last two game, that were not westernized. And it have free Demo on GoG.
Invisible Inc. Little game about stealth, hacking and cyberpunk corporates ruled dystopia. It is really short, very tactical in nature, somewhat X-Com like, but you have to choice wisely what missions to do, so you can finish the game. And the ending was really unexpected for me.
Shadow Tactics: Blades of the Shogun and Desperados III. Really good games, that reminds me of old Commandos games. But they are modern and are made really comfortable for player (if you change keybinding first). Atmosphere is good, story is decent, if you like stealth and careful planning you will like it (but games are really hard some times, so you will have to adapt to a new playstyle or endure it, at least Shadow Tactics was that for me). Both have free Demo on GoG.
Shadow Warrior (2013). Not like old Shadow Warrior, but works fine. Shoot demons, slice demons, survive Serious Sam style enemy waves, explore Asiatic landscapes and demon world. Story is good for this style of game, music is decent IMO. Just don't play second game. I was trying and now I know that was a mistake, first game is better and it is a complete experience.
Ghost 1.0. Pretty cool metroid-like game. And not a parody game, like others made by this team. So they done really good on this one in my opinion. Fun combat, good music, cool cyberpunk-ish world. Only thing I don't like is the last boss fight, which is...well, you know if you know.
Ghost of a Tale. You are a little mouse. You can not really fight, but you are smart, you can hide, you can fool people by changing your costume, so you may not really need to hide any more...eventually. World around is scary (and end up being even more scary), animal persons around are mostly dumb and you have to find your way out of the prison and to your wife. So, I like this game's story and atmosphere, but the end is a cliffhanger, and I am not sure there will be second game.
Teleglitch. Little game about you, small amount of pixels, killing other zombie and mutants shaped pixels. it is really kind of like that, really simple, but complex in a way. Lots of weapons and other useful items, decent story and atmosphere... Even if it is a bit hard on your eyes. Was not in a mood to finish it yet, but game is cool.
Arx Fatalis. You know the game, right? If not, then you should. Epic underground adventure in a post-apocaliptic fantasy world. Awesome in all aspects in my opinion, even if it is hard to run on modern PC. At least it was when I were playing it some years ago. World is good and all caves, gameplay is varied, especially magic, which may be tricky. And soundtrack... And voice acting, which I experienced only on Russian, so don't take my word on it. Really cool game, even if it can be hard at times, at times cause it is old.
The Chronicles of Riddick: Escape from Butcher Bay. Another game you can not buy now it seems, for some reason. Story about escaping sci-fi prison. And Riddick, but mainly prison. And this prison made good. you can bargain, steal, and later kill people and...not people who prevents you from going out. Much better than any movies were.
Rhodan: Myth of the Illochim. And another one I don't know if you can buy. It is a quest and I remember it being really cool and actually beatable without a guide. Based on sci-fi book series about Perry Rhodan, who is kind of aggressive diplomat, that made first contact with aliens possible and safe for both sides, as I remember. I do not remember really much about the game, aside from him being immortal and trying to prevent some catastrophic events connected with that fact. I think this game still worth checking out.
Archangel. Sad to see how other games have same name now, so it is harder to search for it... But still this game is cool. It is a game about defeating forces of hell at several points in history and even in other world. You died, so you have to beat them all. And bring it to their home.
Pilot Brothers. Russian adventure games series, that follows Russian multiplication. Can recommend all of it, especially multiplication, it is legendary really. Games are less legendary, but still good, even if at times logic are somewhere out and first game have one really hard puzzle.
X-Blades. Was also known as Oniblade. Other game from Russia, and for some reason steam page lead me to "this game is not available for your region" page. But I still have a Cd with this game. Competent hack-n-slash game with some magic, platforming and lots of hacking and slashing. World looks good, girl looks cute. Maybe one day I will finish it on good ending.
RunAway. This one is here mainly cause I STILL REMEMBER THE SONG. Really impossible to get it out of my head. And I remember this adventure being good. Not without problems, but it was interesting to play some geek that is slowly becoming almost badass. But not really, I don't really like what they were doing in postgame cutscene. And I never played any other games of the series.
Forgotton Anne. It is here, cause look at this animations. They are cool, they are made good. And environments are made really good. And world is good, and have kind of interesting lore. But ending just sucks. Both endings actually. Had free Demo on steam before, but now I don't see if it exist...
Rent-A-Hero. Some other old adventure, which have no recognition in modern days. And I were almost able to finish it without a walkthrough. Our hero is a professional hero, who is barely able to get some money on this job. But suddenly stakes get bigger and... And you go on fantasy adventure to safe the world.
Space Rangers. But, this game is a second one actually, a remake of it, not original second part, which is this. And this is the first one. Other Russian game with weird distribution model, I have CDs, but don't know how someone can obtain it now. And don't really know if English versions are any good, or if they really exists. This games were good, they have really varied gameplay. You have economic strategy, you have 2D space fights, you have same, but arcade in Hyperspace, you have text adventures and you have real time strategy in the second game. And all of it came together really good.
Star Wars: Battlefront First and Second. Old ones. They are here for you know what reason. Yep, there are two new games with exact same name, but old ones were already good. I played only single player back then, but it was good. And you have all the things SW universe can provide. Cool combat in cool environment. I wonder if now they are still playable with multiplayer. Old Battlefield 1942 was as good, and old Battlefield Vietnam was supergood in multiplayer and have all the good music. They are all together here cause for me they are really one game, but in different decorations. And they rocks!
Extreme-G 2. Was surprised to find this game on steam today. It was my favorite (and only) motorcycle shooting game, I almost beat it too, but my version were shortened. Seems like people think that PC version controls are bad, but I don't think so, they are just too different from modern games. Have really fond memories of it, so may be some day I will finish it.
Ok, so 21 games... Well, more than that, but I think this is already really big list. So I'll add some honorable mentions for games, from which I've played only Demo and be done with it.
Black Book. RPG about Slavic mythology. Interesting story and ok combat system, but I don't like some parts of the game, like main lead's Russian voice acting.
Black Skylands. Cool world, you have your vehicle flying and shooting, basic combat, farming (for some reason) and story I don't really care about, but it was fun to conquer flying islands in the demo, which is really big.
Gloomwood. Really Thief-like game, like first two games. Even if game is less creepy visually, but atmosphere provides some bricks dropping.
One Dreamer. Game about programming logic. Interesting concept and supporting it story is fine too.
Ultrakill. Now this is fun fast 3D action game. And that is all I can tell you about it.
SKALD: Against the Black Priory. Oldschool RPG, it looks oldschool and this is cool. Combat system is simple, but fun. Turn based dungeon crawling is decent too. Story is intriguing.
System Shock (remake). Yep, someone decided to remake it with newer graphics. I've seen old one, but never played it myself. And I don't know if I will play this remake, but it is intense, you really feel uneasy... Maybe it is just me, but think there are people who may like it.
Sorry if I repeating someone, for some of this game I am sure of it. But I think the more you know about good games - the better it will be for everyone. And maybe I will remember some more, but I think I've mentioned all that really needs mentioning.