While offering some new weapons and enemies, these expansions fall short of matching their predeccesor.
The story in each of these expansions follow a different F.E.A.R. team, offering a different perspective of the story as you travel through different locations. However, I didn't find myself drawn in to the story element in either of the expansions, and just worried about where I was headed next. You don't need to play F.E.A.R. to play these expansions, but it will help to understand some of the story elements, and the interactions with some of the characters. Generally they play out with much the same pacing as F.E.A.R. with various gunfights, attempts at scares, supernatural foes, hallucinations, and some tense battles against more heavily eqipped foes.
For some chapters of these expansions, you will be accompanied by a team mate or two which was rarely the case in the original. However they don't often add to the gameplay, and best as I could tell they were invincicble and didn't need protecting when you got into gunfights. That said the majority of your time will still be spent fighting alone. The mechanics and gunplay are exactly the same as before. There are a few new weapons to play with in the expansions, with the VES Advanced Rifle becoming one of my favourites, a scoped rifle that enhances low light conditions. The minigun churns up ammo, but can make mince meat out of your enemies in no time. Another nice addition are turrets that you can lay down, which can be helpful in more open areas to help prevent from being surrounded.
New enemies come in the form of armoured minigun toting super soldiers, soldiers that have reflexes like that can 'slide' when they are shot at to avoid your fire, and a few new supernatural enemies. However, what has been made up for in variety has been more than lost in artificial intellgience. The original game had great squad tactics, and all of that seems lost in these expansions. There were a few times when I saw some intelligence, such as a soldier knocking over a box for cover, but these moments were fleeting. Here, the enemies are much more inclined to come through a doorway one at a time, and their flanking tactics are almost nonexistent, though the level design doesn't allow them much opportunity to do so this time around. Also, some of the enemies are just annoying and feel cheap rather than genuinely challenging. In particular are the enemies that wield grenade launchers or percussive weapons, as they rarely miss whether you are strafing normally or in reflex mode, despite the same weapons feeling useless in my hands. One 'boss' fight in Perseus Mandate is of particluar note in this regard, and I almost stopped playing the game at that point as I mashed the medikit button every few seconds until I managed to beat the fight several tries later.
Graphics are the same as F.E.A.R. so they are dated but still look decent. The main detractor graphically is when there is smoke caused bu explosions or by bullets hitting objects and raising dust, which is on the blocky side. Shadows are inconsistent, with some being solid black (mainly your own) while effective in other areas, such as a 'scare' moment where a light has been knocked and shadows play around a room. Soundwise everything is the same with the weapons packing the same punch, and enemy chatter as it was before. There are some fights that are accompanied by tense music, which then drops off after you kill the last enemy. I don't recall whether this same tactic was used in the original game, but I felt it did the game a disservice. The moment the music dies down, you know you can relax, and relaxation is not the tone these games are going for. I felt it would have been better to continue wondering whether you really had cleared out the area, staying on your toes as you progressed. Unfortunately the game was a bit on the glitchy side. Nothing game breaking, but it broke the immersion. Things such as ambient noises continuing to play after you had left an area, dropped guns rattling on the floor uncontrollably instead of coming to a complete stop, and enemies yelling out they could see a flashlight when I didn't have it on.
The scares that the games throw at you are hit and miss, and after a while you just go through the motions when visions appear, as they aren't often threatening. There were still a couple of times when I jumped, and I did find one of the scenes where you witness the death of a team mate entertaining. Some of them can be a bit disorienting (to the games credit) as you enter into a hallucination, continue travelling, and then come back in to the real world in a different place, wondering how you got there. The level design takes you to a few new places, though in Perseus Mandate you will find yourself travelling backwards through a few locations that were in Extraction Point.
If you haven't played F.E.A.R., I recommend playing that first as it is the better game. F.E.A.R. Files is a mild letdown as it doesn't quite reach the level of the first game, but is still enjoyable in its own right.