This is something I wrote a while back, edited for today, but I thought I would share it with you guys so you can get a feel on my thoughts of it.
Introduction: The game is developed by Bohemia Interactive, and is the 'third' installment of the series originating from Operation Flashpoint in 2001. The fundamentals of the game in 2001 have not changed massive amount to todays work. The game itself is for basically every gamer be it pro or amateur is Hard , it a true military simulation in every sense of the word, this can be attributed to BIS developing a near identical other simulation called Virtual Battle Space 1&2 which are one of the training tools being used today by the US/UK & Auz armies. The terrain which you operate on in arma is nothing short of remarkable, the main map in arma2 vanilla is 250sqkm of eastern Europe based of terrain of the Czech Republic, to say this game is sandbox is an under-statement, you CAN go anywhere anytime you want in whatever vehicle you wish or just walk, dynamic weather , animal life, local population, you name it it has it, one of the improvements coming from the expansion Operation Arrowhead (OA) is that every single building on the map is fully enterable, with many floors, plus the main city map which is 75sqkm of urban area has a fantastic mosque in the center of the city. Finally the most powerful tool of ArmA in my opinion, the Editor, in this immense tool, you can do what you want, you have the maps at your disposal a simple click puts down a group or a snigle unit be it men/air/Armour/sea, there are three factions to choose from both different according to if your playing ArmA2 vanilla or OA which combines both.
Sinlgeplayer/Campaign The SP side of things is immersive to a limited extent, the campaign setting is more than loosely based on the events in Georgia in 2008, but with the added faction of the United States Marine Core. You Task-force a spec-ops unit are sent in in front of the main force to take out rebel positions ect ect , the morning before the main attack. From here the campaigns begins to take shape, you make allies in the form of a friendly guerilla group, and help them take out the bad guys called the Czdaki, but of course they have their own back up...the Russian federation. This is what is meant when i say immersion, it has that dark dangerous feel of the cold war, as did the previous games. One of the special things about the campaign is that it is very dynamic, there are times in the mission were HQ will ask you if you have had enough or ask if you can do another objective, its your call if you want to, however....every mission shapes out the final out-come of the campaign even from early on, from what i can remember there is four final endings that can happen, the missions in the campaign list have different outcomes, so three different types of the same mission, if you get me . Along with the campaign, BIS also have given you around 8 extra missions to play as well, along with training to all parts of what is needed to learn. Action in the campaigns can be anything and everything, leading a platoon towards machine guns, coming up against tanks, planes helicopters, or sometimes you be it US/UK are in the tanks, or the fighter jets, or indeed infantry in which, there is a tool called high command can be used which is basically you controlling a massive force, and maneuver them about the field of battle from your map. Battles in ArmA can be epic as you can have i think around 2000 units on a map at one time so no holds-bar.
Multiplayer: MP on ArmA is another good experience, there are several modes of gameplay, some made by bis others by the community in the editor. PvP seems to be popular at the moment and will grow as famous Dev's Project Reality are now coming into the fold. For me ArmA is not really a pvp type game it lacks the fluidity of games such as bf2 or cod, its much slow pace. The bulk of my time in arma is spent playing coop, which is great fun. The campaign is available in coop both ArmA2 vanilla and OA. However missions and new campaigns are released everyday online so there is an unlimited amount of fun to be had. As for me i am part of a ArmA gaming unit, and we have coop nights and training nights as do the vast majority of other clans throughout the community. Coop for me wins really because the AI are very clever in combat and do all the things you would expect, i.e. if you have a larger force than the AI , then they can pop smoke and try to flank you ect.
Community/Modding/mission-editor: One of the things to set arma out from the others is its community, it is large to an extent, the modding is really on a par with the BIS dev's themselves the mods extent from new tanks planes and units to whole new maps and complete conversions, i myself work on the Vietnam mod so you can make the game be about whatever you want, and there's always mission and campaigns to go along with these. Conversions such as WW2, Vietnam, cold war ect really do make the game last forever. The editor as i said before is a powerful tool, and if you take the time to learn it which is hard, (scripting, coding ect) then you can make missions and campaigns of your dreams, its really no stop to its power, I've seen mission and camps by the community before based on films, with all the appropriate cut scenes and sequences. Other great additions to the game are mods such as ACE which adds an immeasurable amount of new units, plus new weapon ballistics, backpacks to put gear in stamina, first aid models ect. Modules also are a decent part of the game, they can be set down in the editor to populate it or cause certain scripts to start working, i.e. civilian script or car or animal module will populate the map (remember we're talking massive maps) with all of these, others consist of UAV module, weather, first aid, and they all are simple enough to use. You may have noticed I have not mentioned Dayz once yet, that is nothing against the mod itself its a fantastic new thing brining in more money and players to ArmA , however the fact I have no mentioned it I believe is credit to the base game itself.
The Rest: Aside from all its superlatives, the game(s) do have set backs, some bad bugs do exist in the game unfortunately, AI behavior can be sporadic, with flying as well they don't always to what their told.
Conclusion: The game as its pasts have once again become the forefront for military simulation, its unforgiving mind-numbingly difficult, but behind it all lies something truly spectacular of which i have not seen before, the graphics are fantastic, they look real, the detail is great, and the story, is good enough but the game is so much more than its campaign. Well i do hope you enjoyed my review its abit jumbled but i thought i would share the game with others who may not know of it, along with others who have played it i hope my points it home, so once again many thanks for reading.