Patient Gamers

S.T.A.L.K.E.R.

All three base games. So many mods.

The zone feels vast, lived in, dangerous.

The ai is dynamic, moving through an area once you mind find a group of friendlies engaged in a firefight with a powerful psychic mutant, and other time find an eerily peaceful vista.

It's not a power fantasy. On harder difficulties you're always on edge when you're exploring even with end game gear. A single bullet from a sniper or a random pack of wild dogs can easily end your run.

Highly recommended of you've never experienced it before.

If you haven't already, playing Black-Mesa -> Half-Life 2 -> both Episode 1 & 2 are the perfect examples of what you describe. So many details and stories in all the levels, and you are just a guy passing through

Prey (2017) has a great level design. It's one giant interconnected space station that can also be explored from the outside. Different areas all feel very organic and actually liveable.

The Deus Ex series is good at this. Instead on having a big vast game world they have a condensed area filled with tons of details used for storytelling. You can go into a lot of places like apartments and it says a lot about who lives there. How well kept everything is, what posters they have, the station the radio was on, the stuff in their nightstand etc.

SWAT 4 also does a great job with the environments. One memorable level is where you are trying to arrest a suspected serial killer. When you approach the house everything seems...underwhelmingly okay and the mom pleads with you to not take her son because there's clearly a mistake. As you clear more rooms things get messier with some traps and blocked doors among the clutter making it a claustrophobic and dangerous maze. Eventually you find rooms dug out from the basement with a girl who had been missing for a long time as well as makeshift torture rooms and plans to capture and kill more. It's just a slow descent into their madness and it's quite the experience to play.

My top suggestion:

Halo 3: ODST

The entire game takes place in a single city in a single day during an invasion, with the player having flash-backs / flash-forwards as different characters so you can see what and how the city evolves over time.

There's also a secret story (called Sadie's story) hidden in the terminals found around the city that follows a civilian and a [REDACTED] during the moment of invasion. If you're able to complete Sadie's story, it tweaks the 3rd act of the game.

My other suggestions:

You seemed fairly set on FPS games, but they're not the only ones that have the same dark environmental story telling like Bioshock, SOMA, and Alien Isolation.

These are going to seem weird but stick with me here:

1. Metroid Fusion
2. Frostpunk

Metroid Fusion is a platformer. So what? How can a platformer have that same kind of feeling? Well let me tell you, Metroid Fusion is one of the rare games that was able to do horror and do it without relying the easy immersion that FPS games tend to lean on. I never knew that a platformer could be terrifying and it was a wake up call for me, because I had never even considered that a non-FPS game could elicit those feelings.

It's a gameboy advance game so super easy to emulate on a computer, you'll want to play on a keyboard or a gamepad, a touchscreen overlay can't keep up with the controls you'll need to pull off to survive. Go into it blind and ~~despair~~ enjoy.

Frostpunk.

It's basically a Victorian steampunk version of The Day After Tomorrow. The world is freezing. You're the leader of a charge of a city fighting for the resources to survive. You are from the last group of survivors. If you make a bad choice, everyone dies. The story is told through random events that pop up during the game where you have to decide which choice you want to go with, while exploring the derelict ruins of the other failed survivors to try and gather more supplies.

Most environmental story games where you can see something has clearly gone wrong tend to be horror, where there is a threat that you can point to and say that is the bad thing that must be dealt with or escaped from. Frostpunk goes the other way. It is not horror, Frostpunk is terror. The climate is the threat. There is no escaping it, there is no way to shoot it with a gun, or a special weapon. It is ever-present, and it gets worse and worse each day that passes. It is a building tension that keeps twisting, getting tighter and tighter, where you will be forced to make hard decisions. The stress level only goes up. Whatever you lose you will not be getting back, and you're only able to keep a few things. What will you sacrifice to make it to the next few days.

Frostpunk is the game equivalent of being a pilot in the cafeteria of an airport and seeing an emergency alert on every news station that a 1 mile high tidal wave is approaching and will hit in 30 minutes. And each minute that passes, the more desperate people will become, and the worse your situation will get.

I wish I could tell you Destiny. The original game, with the original maps and through a couple expansions, had great level construction and felt like you were exploring alien worlds. But because it's always online, they threw away all the good levels and replaced them with weird nonsense.

If you're open to third person, Sniper Elite (at least 4 and 5) fits the bill. It's not one of the third persons with your character in the middle of the screen and the perspective isn't that far off from first person. They're more stealth than run and gun but you can do the latter if you want. But you have enemies patrolling bases, driving patrols, frequent flyovers, and various notes and things to discover.

I can't think of a first person game any better than Doom in terms of world building that you can still play.

The Thief trilogy have some of the finest environmental worldbuilding around, highly recommend them if you enjoy stealth games.

I'm surprised you don't mention any bethesda titles (fallout3, oblivion, skyrim..) since they're just an already existing world you're put into with their own factions an politics you can integrate and influence

Going to mention F.E.A.R 1 and to some respects F.E.A.R 2, its a first person game that lets you see your feet for one, but seriously they did a really good job with replica AI -even though they are clones they have personality - like making cover from environment, trying to use environment to get away from a bad situation - like crawl under blocked door's crawl space or shoot and run while getting to cover

Your character has an in-game reason to have slow-mo which is really well done in the I can throw a grenade, go slo-mo, hear the enemy crap its pants and shoot the grenade,see the air around the explosion expand and witness an appropriate blood and gore shower.

They comment on your speed, panick when they run out of ammo when you rush them and try to flank you if they can.

It has some horror elements as well but usually in service to the story as First Encounter Assualt Recon is meant to deal with shady stuff and F.E.A.R 2 had a really cool school level.

Level design for the first 2 also was pretty fluid with reasonable area transistions that made sense how you got where you were at even when it is mostly just a point A to B with some light exploration for secrets or weapons

F.E.A.R 3 is meh, had some fleeting good moments and some answers to questions from the first 2, but overall felt like a lesser game than the two preceding it. It lost a lot of soul and felt more robotic in design

It doesn't really classify as FPS, but Witcher 3 was great in that way, and also Mass Effect imho

Plugging the metro series

GoldenEye/Perfect Dark had great environments in the single player campaigns. Multiplayer arenas were a bit more generic though.

Doom 16 feels way more like an arena shooter than infinite for me. I think my problem was I wasn't invested in the story and relished each combat encounter.

It is up there in years but system shock 2 is an amazing example.

I just finished playing Deathloop for the first time and I believe it fits your criteria. Very Bioshock, except 60's pop art instead of 30's art deco. I could spend hours just wandering around the island exploring all the detail they've crammed in.

Actually Doom 3 has something like that going for it at least at the first 2/3rds of the game. And is of a big submersive help all of the pdas that are realistic enough as to make you feel in an actual mars base with people working there. But also playing thtought it is honestly a miserable experience since darkness plays a big part on the game to the point that lots of places are pitch black, since it leans more into the horror aspects of doom, witch sound good on paper since hell invanding the mortal plane is a really scary situation to be in if you think about it, but the games goes about the horror aspect by giving demons some horrible and disturbing sound effects, specially the imps with some very high pitch screeching, and it really works for a while but it becomes more annoying as time goes on and just becomes mentally opresive and draining to play as it makes me feel so disturbed that i must stop playing it after a while and i even started having nightmares some times. But the gameplay is very solid, rather simple but solid, while you get enugh arsenal to destroy mars, the monsters drain your resources kinda faster thatn what you would think, and you kinda have to manage what weapon would you use aginst what monster and or situation, and constantly have to explore the facility in order to keep your amo pool and options full and accesible, now dont get me wrong, Doom 3 is an action game with horror elements, not a survuval horror, but the design choices are subtle enough to keep you on your toes. So i recomend since it fits in your requirements quite well, but be warned that its not for the faint of heart. I also recomend you system shock 2, havent played it but i heard it has good world building.

I haven't gotten that far in Outer Worlds but I think has amazing world design. It is built by the legendary Obsidian Entertainment after all.

Northern Journey for sure if nature ambience is your thing.