Natural Selection 2

Over a decade after its release, you still can't get anything quite like Natural Selection 2 anywhere else. But for everything original about it, its biggest problem is far from unique.
Natural selection is a cult classic. And like most classics, much of the playerbase has already evaporated and moved on to other things, leaving only the cult. They boil down to only the most elite, die-hard, cut-throat players, concentrated into about 3 servers. Actual natural selection at play, if you will.
Now don't get me wrong: assuming you get people to play with, many of them will be plenty accommodating and willing to give you helpful tips. It's just that, in my experience, even then you can't really shake the feeling that they're pretty tired of explaining this stuff and that they wish they were playing with someone who actually knows what they're doing. Their good will slowly eroding as they turn into players... less friendly to newcomers.
Playing NS2 with the other people who still do is a *task*. I recommend it only to you if you are as patient and open to your fellow player as the veterans will have to be with you. To play a game that has calcified as much as this one is honestly, actually stressful. If you see getting past that as the big ask it frankly is, I'm afraid that the amazing game waiting at the end of getting the hang of things is not for you.

After playing this game for 3500 hours, literally 5 months of my life. I guess I should give it a review.
This game is certainly unique for many reasons. For a start, the game is inaptly named “natural selection” which is a cosmetic make-up line.
Anyway; it's like a hybrid game of the films ‘Aliens’ and ‘Starship Troopers’.
It's predominantly FPS of Aliens versus marines in an enclosed map where both sides fight for territory and resources. The more resources a team has, the more and quicker weapons and upgrades can be obtained.
The stand-out feature of this game is that both sides have a commander who sees a Real-Time-Strategy (RTS) top down view of the play area. The commander controls the upgrade choices and allegedly gives out instructions for players to follow.
The game's last on average 20-25 minutes, there is a finite end.
The game has quite a steep learning curve, particularly the Alien weapons, upgrades and different creatures (lifeforms). I'd recommend you play the tutorials first and start with marines; their weapons and upgrades are easily more intuitive.
I would strongly recommend not going commander until you have at least a hundred hours of gameplay experience. Players are extremely unforgiving of mistakes the commander makes or what they perceive as an incorrect strategy or incorrect choice of upgrades.
The game is still very much alive and there are usually 6 or so full servers around the world. You will certainly be able to play. The players, as they are usually hardened pros, can be impatient with new players. My advice is just ask questions politely and stick at it! The reward from understanding the game and the intense ferocity of play is quite an adrenaline rushing.
There's a reason why the players get so intense and upset, it means so much to win and feels so darned bad to lose.
Understand, this isn't ‘capture the flag’ LoL.
I have given this game so much of my game-playing time because it is a fast paced, complex strategy game with seemingly endless strategies and counter strategies that can be tried.
The developers have seriously gone above and beyond themselves to design, plan and code this game. It would be great if there were more like it but unfortunately that is the reason why I have stuck with it for so long. It truly is a unique game.

For $5 this game is an absolute steal, still has an active community, addicting competitive fps gameplay on the marines mixed with movement mechanics that would make "bhoppers" blush granting extreme mastery as aliens. Even if you never play Commander the game is enjoyable. If you do play commander, you will find a nice level of depth that RTS players will enjoy. Newbie friendly servers are pretty popular and always at least one is full.
My main complaint is the netcode. Even at 90ms you get killed around corners as aliens a lot. No killcam means sometimes you experience deaths that really make you scratch your head. The developers have ceased active development on this game so don't get your hopes up. There's also a matchmaking mode that is totally broken, and apparently only populated by idlers who want to receive the rewards, so you have to use the server browser and you will never experience those rewards since they never enabled the progression for non-matched play. What's there is fun, despite these flaws.

NS2 made a huge mistake compared to NS1. It tried to be an esport, or at least be a more competitive shooter and less of a lobby shooter. The community has become very... elite over time, I won't go as far as calling it toxic. They're just good at a game that requires close communication and lots of game knowledge to be successful at, particularly at lower player counts... which is an issue, because NS2 doesn't allow for larger lobbies or they never took off like NS1's did. It's much easier to be new at a game when there's a lot of people on your team, as a few bad players can't tank the whole team. In a 12v12, 2 bad players on a team will throw the entire match.
This game would be great if the devs increased the scale and scope of it rather than tightening it. It's very competitive, very fun and very skill based which is great for a 5v5 arena shooter and awful for a FPS/RTS hybrid. This game needs easy gameplay with a meta thats hard to master, not both hard gameplay *and* a hard meta. Sadly, it's largely abandoned and too late for anything to be done about it. Still, it's only $5 which is cheaper than a meal at McDon's these days so.. yeah. Recommended because of inflation!

A tactical multiplayer game where marines and aliens fight for survival. It's mostly a fps until you sit in the command chair, where you get to watch the map from above. Communication between players is highly recommended.

The community servers are alive and well. There are dedicated noob servers where we will aggressively educate you on how to command. This game requires substantial teamwork and coordination. Get a mic, ask questions, and be willing to take feedback. A lot of the perceived toxicity just comes from invested players who get frustrated from an uncooperative commander and/or and uncooperative team. But when the team comes together to push a hive or rush the command chair, you will experience some of the best satisfaction a game can deliver.

Good game with good innovative gameplay that blends extremely well the fps and rts genre. The gameplay is fast paced and fun albeit not very well balanced and you can see this visibly in the stats with a 60% win ratio for aliens in comp play and even worse in casual play (from my experience aliens win 90% of the time even with mid teams, I was fooled by having 3 consecutive good games as marines and then hit by loss by loss as marines on my first public games).
The close quarter map style puts a heavy advantage on the melee-centric aliens team with their dirty ambush tactics and fast hit and runs whilst the marines would be lucky to survive against a grunt alien, who are always faster, higher health and heavy hitting. Guns in the game rarely kill fast enough before you get killed and you would miss a lot playing first time since aliens love jumping around and missing a few shots can spell your doom. Without a capable team, you are branded for defeat; not to say aliens don't need a good team but they less rely on such, often going solo. And since it's just much easier as aliens, teams are often lopsided, and newbies taking the marine side thinking it default or going for an alien vs predator feel. Marines also have to manage their resources much more vigorously, having only 1 class they have to buy equipments which are very expensive compared to the aliens' evolution and coupled with the survivability of the marines which is much lower.
The core gameplay loop is simple, you have a commander that directs you and supports you, but he does not manifest on the battlefield and can only place blueprints and manage resources. The goal is to destroy either all the hives or the command stations of the opposing teams and by capturing nodes you can harvest resources to gain more equipment to gain an advantage over the enemy.
Now there consists of two teams and their unique style:
MARINES:
The marines are the ranged faction, having basically no melee but instead owning an arsenal of guns and equipments. The gunplay is very similar to half life, with emphasis on action and speed and no aim down sight, and a big thing you will learn is to stick together and take advantage of concentrated firepower to suppress the aliens and keep your distance since lone marines never fare well. Marines also have exo-skeleton suits that gives them more armour and a twin minigun or plasma guns, both can devastate the aliens, but it is still a glass cannon and a few grunt aliens can take a lone exo down with ease. The marines often have the advantage and thus can force the aliens to fight on their grounds and attack aggressively and whittle them down this way, however, once caught in melee it is very difficult to disengage and fight back and it often means certain death. Also marines have to build the blue prints their commander built which means they have other tasks other than fighting, though they do make up by everyone being able to fix armour and buildings.
ALIENS:
Aliens depend on melee, surprise and speed and they have 4 evolutions. The grunt Skulk, which is fast, can stick to walls and climb tunnels, it makes them very versatile, dealing massive damage with their chompers (2-3 hit normally) and can they can scout and late game they have a suicide bomb ability with no counter making them a cheap way to deal heavy damage even late game; just imagine braindead aliens bhopping their way into your spawn just to spam that attack, you might survive the first yeah but there are waves of them. The next two are the Lerk and fade which are the assassins so to speak. The lerk can fly and have a decent ranged weapon and has high health making it a potent hit and runner whilst the fade has decent health and can dash out of range quickly, making it another potent hit and runner. Unpleasant. The gorge is the support and it kind of does what all marines can do: fix armour, heal structures etc but it can also act as an engineer and build defenses, which the marines cannot. And finally the onos. A monstrous breeding of gorilla and rhino, this abomination can deny marines an entire area based on just how tanky it is and how deadly it is to normal marines. Very annoying.
Anyway, this game is kinda dead and the bots are bad, but its worth playing with friends and sometimes there are servers and if you are lucky you can find a good team. My main gripe with it is just that Marines are way too underpowered and need a lot more skill and coordination to get it to work. Still fun game though