Arma 3 is the type of game you will never find anywhere else. It is an Awesome game, with a few major drawbacks.

The idea behind Arma 3 is a "military sandbox". What this means is that the vanilla game is great, with a lot of content and gamemodes you can play with. Outstanding realism, good graphics, and awesome huge maps. Casual players will love some of the classic gamemodes, from Team Deathmatch to Role Playing, this game has it all.
But for me, the real magic comes with modding: We are talking about tremendous amounts of different gamemodes, maps, buildings, stories, scenarios, factions, sounds, physics, vehicles, planes, helicopters, guns, uniforms, accesories and more, all created by the community on top of the vanilla game and that you can play for free (as long as you have the game obviously).

But i really love about Arma 3 is that community mods give the game a totally different experience while playing. Playing with your friends using some mods is awesome. I even joined a public clan that recreated WW2 using Iron Front Mod, and it is awesome.

That said, Arma 3 present a few drawbacks: first, it is extremely painfull to get used to the hundreds of controls the game has, and you will probably need someone to help you on your first time. Good news, Arma 3 is known to have one of the best communities, and it is true. People are happy to help and guide you.
Arma has a big problem with optimisation, so be sure you meet the recomended specs, but expect casual framedrops.
Some of the controls are a bit counter-natural, like the in-game menu to open doors, which is done by scrolling down, selecting the actions you want to perform and then press space. With a little practice, you get used to it, but it is true that it is surprisingly hard to get the hand on everything, specially when you play with mods, whitch you probably will at some point.

That Said, Arma 3 is still one of the game that has an average 228.25h of playtime, and it is certainly not only one of my favorite games, but also a game that anyone can enjoy.

I give it a solid 9/10 despite the bad optimisation. Despite all the issues that this game has, bohemia has created a game that is definetly the best and most complete FPS game yet.