Solid tactical shooter set in the Middle-East, focused on close-quarters combats. Can be a little confusing to new players, but any efforts will be rewarded.
+ well-crafted environments
+ Steam Workshop support (check the "Intense Realism Soundmod" to get the full experience)
+ lots of maps and weapons (regular free updates)
+ no unlock or grinding: full access to all weapons/items right from the start
+ good shooting feeling
+ proper bullet penetration and suppression
+ proper smoke grenade (much less silhouetting than in other games)
+ Co-op mode: highly recommended for beginners and veterans alike
+ (co-op) proper enemy AI, that even knows how to use grenades (including smokes) *AND* RPGs very efficiently
+ solid voting menu: change map, vote kick, change difficulty (co-op), change amount of enemies (co-op)
+ VoIP can be heard (low volume) by enemies at close range
+ order system allowing the 2 Leaders to mark a window/door/location (attack/defend/watch/suppressive fire)
- too many game modes makes it confusing for new players
- the gear selection menu is a bit confusing for new players, who don't realize they can remove the pistol and extra ammo to get AP ammunitions or a better aiming system
- the difficulty on high-population PvP servers can be brutal at first (I recommend trying the Co-op on Normal difficulty first to learn the rope). It is possible for an experienced player to kill new players without being easily spotted, making it rather frustrating at first
- some maps are too smalls for 16 vs 16 players, making maneuvers such as flanking nearly impossible when high-pop servers are fully filled
- no mantling system (climbing over obstacles), hopefully maps rarely requires that
Now, the obvious comparisons:
1) It's not ArmA: the maps are smaller and often feature urban environment. Average size is about 2 to 3 times your usual CS:GO map.
2) It's not Rainbow Six: Insurgency provides more freedom of movements, you can sprint around with ease (but you might get shot doing that), without sacrifing your accuracy like in R6.
3) It's not CS:GO: weapons are more lethal (more accurate, more deadly), maps are more complex.
4) It's not (really) Red Orchestra 2/Rising Storm: much less sniping at 100-150 meters, more close-quarters combats and flanking opportunities.
TL;DR: RO2/RS in the Middle-East, specialized in CQC. Is good.