This game had so much potential but it lacks so many things you'd expect every run of the mill FPS to have
The single player and multiplayer portion of the game let you play as all three species. However in both single and multiplayer, it is obvious that certain species got the short end of the stick.
Singleplayer wise the game is very VERY very VERY repititive. You play as three different species. However, you go through the exact same areas of the game three times. To make it worse, you fight the exact same dreadfully awful enemies repeatedly throughout each campaign. In the marine campaign, you fight aliens for the most part and then the occasional android towards the end. There's the little face hugger alien, a brain dead predator battle, and a large alien vs predator hybrid, but these are few and far between. 90% of the game you'll be shooting aliens. The human campaign is also hindered by going through the same narrow hallways, stairways, and elevators repeatedly. A perfect example of copy and paste segments. However, it is a decent length (the longest of the 3 at least), and there are some intense moments that come from feeling like you are the prey. Another complaint I had with the single player portion of the marine campaign is that the game has these audio diaries very similar to what you'd find in a Bioshock. At first, I thought it was a cool idea. However, that quickly faded when I found out that you have to pause the game go to the menu which totally sucks you out of the action to listen to these things. My last and biggest gripe with this game is YOU CAN'T CROUCH OR AIM DOWN THE SIGHTS. Seriously?! I want you to imagine being in a battle where their on boxes are all around to take cover behind but you can't because they decided it was unecessary. Sound lame? It is.
In the alien campaign, you fight predominately marines. However as an alien, you only have a melee attack. You can use a light attack, a heavy attack, or a sneaky one hit kill attack. You can crawl on any surface as an alien, which varies up the gameplay a little bit but, you won't need to with this brain dead AI. Oh and one more thing, the alien campaign is probably 1-2 hrs long so on the plus side your misery will be ended sooner than later. Howver even in those 1-2 hrs you'll do the same chomping of human electronics over and over again.
The predator campaign has you fighting a good mix between marines, aliens, and androids. The predator gadgets, which include mines, spear, shoulder cannon, and battle disc, help give the game some variety that the other campaigns seem to be missing. The vision modes look great for the predators. However heres glaring problem with this game. You fight aliens right off the bat in the Predator campaign. However, you don't gain access to your alien vision until about 1/2 way through said campaign. This game is ridiculously dark, which I wouldn't mind if I had access to this alien vision mode right of the bat. Therefore, you end up spending the first half of the predator campaign swinging you fist around in complete darkness hoping you're hitting the aliens. The predator campaign is longer than the aliens but shorter than the marines.
Storyline wise, all three campaigns are bad. It seems like Rebellion was going for a theme like the movie Vantage Point. By that I mean even after beating one campaign, you'll really not know what the heck is going on. To fully grasp the storyline, which again is bad, you'll have to play through all three campaigns. This leaves the storyline feeling very disjointed.
So now to the mutliplayer, which some claim saves this game from being a total disaster. They are right the multiplayer saves this game from being a total train wreck and turns it into a mediocre game. The mutliplayer can hold up to 18 players, usually only lags when playing a moving map called pyramid, and has numerous game modes. Most of the game modes are standard deathmatch, team deathmatch, king of the hill variants. Howver, there are two, infestation and Predator hunt, which are unique to the game.
In infestation, everybody but one player starts out as an alien. When you die as a marine you become an alien. This game mode can be fun when playing with skilled marine players. However, most of the time the after half of your team has been turned into aliens the game turns into a slaughter and is over within 30 seconds leading to a very anti-climatic feeling. In predator hunt, one player is the predator and everyone else is a marine. If you are the marine that kills the predator, you then become the predator. However as the predator you never feel like a hunter, you feel like the prey which just seems backwards. During most of predator hunt, I was a marine bored to tears just running around mindlessly waiting for a blip to go off so I could find the predator and hopefully kill him before my teammate did.
Other complaints with mutliplayer include the ridiculously long sneak kill animations. These animations are brutally fun to watch. However, they don't fit into a mutliplayer setting. This leads to Gears of War style trains forming where people just get stabbed in the back repeatedly. Also, I'm not going to say the game is unbalanced but it woulldn't be too far of stretch to say it. The Predator has a shoulder cannon that can lock onto you and a jump attack that can knock you over. Each of these attacks are very powerful and as a human and an alien leave you with little to no defense against either of these. The Aliens has the steepest learning curve as they have no ranged attack and must sneak up on their enemies or get stomped. People will tell you that being able to crawl on all surfaces gives you an advantage but most gamers probably won't know where the heck they are when climbing on surfaces. It is very difficult to control.
In conclusion
+ When playing as a marine, you get that intense feeling of being the prey
+ The sneak kill animations are brutal
+ The mutliplayer is worth trying out
- Can't aim down the sights or crouch?!?!
- Single player is short, repetitive and all round one of the worst I've played
- Multiplayer isn't unbalanced but it's certainly easier for some species than others