This game has many great aspects that hide the negative ones. Likewise, negative aspects hide the good ones.
The game intro will leave you wanting for more. The game's story progresses through rendered pics after each level, and this is where one of the battles I mentioned occur. In the first few levels, the story is pretty much simple. The area is infected with a fast spreading virus and you're the HAZMAT team member sent to clean up the mess along with your team. This virus is affecting every human in the lower levels. Then the obvious happens, your members are no longer with you, you discover more mess as you go below. Then the story takes a twist that is the highlight of the game. Without spoiling much, I would say, as you appreciate the story, it suddenly gets awkward near the end.
Graphics : 10 / 10
The Area 51 is not just the "research facility" that you know about from movies or other sources but here, it comprises of vast levels, testing facilities, underground areas and more. They are well designed and the graphics are sharp. The characters look crisp and the models are great. The enemy has many animations, they have lots of animations depending on their situation and overall they look good. The later levels have superb design and it will make you stop for a moment ocassionaly to stare at the wonders. The weapon models are highly realistic too. There are no framerate problems and the game runs steady. Finally, the alternate vision does a good job of depicting the surroudings.
Gameplay : 10 / 10
You play as a HAZMAT team member Ethan Cole. Initially, you begin the game with your team and you find it a lot more easier as they can take out most of the ememies for you. They are smart too. They will run for cover when swarmed, warn you for enemies advancing direction and they are quite talkative. As you progress, you get infected too, giving you new abilities such as a melle attack, parasite attack, etc. You cannot use weapons in that form and the mutant form lasts as long as you have "mutagen", indicated by a bar similar to and above the health bar. These really add to the gameplay as sometimes, the mutant form is the only way to go through.
The weapons in Area 51 are very few, which is bad. You have the standard pea-shooter, err...I mean pistol, the SMP, shotgun, sniper rifle and a couple of "other world" weapons and grenades. Thats about it. The could have been room for more but on the bright side, the weapons handle and feel great. The lack of weapons is filled by the mutant powers which you'll gain more as you progress. Then again, there are just a couple of powers. See what I mean by battle?
The enemy AI is smart. Most of the mutants are unarmed but you will come across many weilding weapons. These mutants are clever enough to cover their faces when you go for a headshot or aim your flashlight on their faces. In the later levels, you will have to kill humanlike emenies that have weapons, intellegience and even camaflaouge. These are the "Illuminati" and they can give you a tough time on medium or hard difficulty when they come in groups. They are challenging ocassionaly. But here begins another battle between the good and bad aspects. None of the enemies change their tactics or get tougher in any part of the game. Once you know how to beat them, you can do it again. There are few boss fights and they are easy.
Sound : 9 / 10
The voice acting of David Douchonvy as the main character is simply awesome. He does a good job but I cannot say that for the rest of the characters. The redio chatter is boring and since it is constant in the initial levels, it gets annoying. The voice over of "Edgar" is great too.
The mutants have a distinct growl that can be heard when they are close. This is great to keep player on theit toes. whereas those damn Illuminati dont make a sound at all. Then comes the bad part. The music is repetitive and you'll hear the same "fast theme" when a heated battle occurs. Other than that, there hardly is any music. However, the ambient sounds are quite impressive.
Value : 6 / 10
The multiplayer is boring with not many modes. The story mode is of average length, around 8 hours or more and there is no reason to play it again. There are some unlockable videos in the extras which give more background info about the happenings of area 51, how and why the virus outbreak occured. These videos can be unlocked by "scanning" some specific objects in the story missions by your scanner. Not much I'm afraid.
Overall, this game is a great one and if you dont want to own it, definately rent it to check out the story and its quite fun to play the single player while the story lasts.