This game got savaged by critics and players alike when it was released for being too much like a discount Far Cry game, despite being an indie game from a small company in Eastern Europe. The comparisons to Far Cry are fairly apt - the game features a small open world for the player to walk, drive, or zipline through, there are outposts to clear and sidequests to engage in, and a small variety of collectibles to gather. Sniper Ghost Warrior 3 lacks the more unique and fun features of Far Cry, though, such as animal attacks, hunting, flight, weapon variety, customization, the scale of the world, and a good story. What sets Sniper apart, however, is the gunplay mechanics.
The conceit of Sniper Ghost Warrior 3 is that it has realistic bullet physics modeled into its weapons, and the missions focus on stealth sniping missions where the player must travel to a vantage point and shoot at his targets from long range. Had the game kept this focus and not forced an open world into its design, it probably could have avoided all the negative comparisons.
In Far Cry, the silenced sniper rifle is one of the harder weapons to obtain because it is almost overpowered, but in Sniper Ghost Warrior it is your primary weapon. Sniper Ghost Warrior tries to balance the effectiveness of this weapon by placing a large number of counter snipers and mortars on the enemy posts, and by balancing the AI around hiding behind cover and spotting you from afar, which in theory should force the player off their sniper perch (but in practice never really works right).
But the mechanic that really makes sniping far more fun in Sniper Ghost Warrior is that the bullet is modeled as an actual projectile which realistically travels through the air, so the player must account for the travel time and lead his targets. Wind resistance, direction, and bullet drop are also taken into account, and the best way to use this mechanic is to turn the "aim indicator" off, since it shows you exactly where the bullet will land, thus negating the whole point of judging those variables for yourself. If you make a wrong judgement and miss, the report of your bullet will alert your target to your presence, which I still find exciting even if I missed. To me, it is far more satisfying to see the bullet actually fly to my target rather than instantly hitting them, and I'm not talking about the slow motion killcam, which is actually less satisfying to me than just seeing my target drop from a well aimed shot.
In the Far Cry series, all the bullets are hitscan, and I don't think they're even affected by gravity, which means that they're essentially the Railgun from Quake, and they're serviceable in an action context but lack the complexity and thrill of sniping from Sniper Ghost Warrior.
There is another sniper game series that opened to much better reviews and always gets compared more favorably than the Ghost Warrior series, and that is Sniper Elite. Sniper Elite 4 also has large levels that function as pseudo open worlds, a stress on stealth and long range gameplay, and a calculation of wind, distance and bullet drop in its sniping mechanics. One thing it does far and away better are the many different ways you can kill your targets - you can use bullets to blow holes in gas tanks, engines, tires, exposed grenades and more, leading to spectacular explosions, you can drop heavy objects onto your opponents, trick them, bait them, and do so much more.
Despite all this, I consider its actual shooting mechanics to be lesser than Sniper Ghost Warrior's, because the weapons in Sniper Elite are all hitscan. What this means is that even though you account for distance, wind direction and bullet drop, none of it really matters because all it does is make you adjust your aim a little on a 2D plane, as in simply choosing a different (x,y) coordinate on which to place your crosshair, rather than meaningfully visualizing the path of your bullet. Sniper Elite's method of balancing this is to make your bullet slightly inaccurate unless you hold your breath for the accuracy to gradually increase. Unfortunately it also has an aim indicator, which I always turn off.
Also, I have a few random complaints against Sniper Elite, such as its 3rd person perspective in which the character blocks your view of the weapon, and the fact that cycling the bolt and reloading the magazine do not cause the player to scope out. Where Sniper Ghost Warrior plays like a discount Far Cry, Sniper Elite plays like a discount Metal Gear Solid V: The Phantom Pain. The latter game actually does a lot of things right that Sniper Elite does wrong. Metal Gear gives you nonlethal options to confront a level and there is way more interaction with guards in terms of interrogations, holdups, and combat. "Aiming down sights" in MGS is required since without it the player character will use his fists to strike or throw an opponent, in Sniper Elite he is always holding his weapon so why does he need to go into a special aim mode to fire? MGS also gives a first person view option which Sniper Elite lacks except technically on rifle scopes. Metal Gear also pseudo models the necessity to lead your targets by changing the calculations on bullet hit for moving targets, which Sniper Elite doesn't implement. Also there are weirder, more fun weapons in Metal Gear and the standard tranquilizer pistol is an actual projectile weapon.
The only other game series I know of with projectile sniper weapons is the Battlefield series. In fact it was my experience sniping in Battlefield 1 that compelled me to find another game with deep sniping mechanics, as Battlefield is multiplayer only and as such has a shelf life and subjects you to other problems if you just want to enjoy the game, like network lag, finding a server, finding a good team, etc.
Sniper Ghost Warrior 3 is an indie game masquerading around as a triple A studio title, and that becomes noticeable once you see all the rough spots just underneath the surface. I actually commend the development team for taking on such ambitions and aiming for the leaders in the industry, rather than being an intentionally budget title like most indie games. The open world is the critical flaw and I feel that if they had focused on making a pure sniper sim the game would have been better received. The development team did talk of their passion for emergent gameplay, and the earlier Sniper Ghost Warrior games were criticized for their restrictive linearity, so I see why they experimented in this direction. While many better games exist and do more than what Sniper Ghost Warrior 3 does, it does one thing that they do not do and does the pure sniping much better than its competitors.
*as an aside, I don't know if the pistols and assault rifles in Sniper Ghost Warrior 3 are hitscan or projectiles so fast that they seem hitscan. The enemies don't move or strafe fast enough for leading them to become a necessity, and with realistic bullet velocities its hard to discern over short ranges anyway. For the sniper rifles it is easy to see the bullet travel with a long range scope, however the same is not apparent on unscoped or iron sight pistols, rifles and shotguns.
*the best difficulty to play Sniper Ghost Warrior 3 on is the second-hardest. Realistic difficulty makes most weapons one shot to kill, which forces players to stay hidden in stealth longer. While that might be more enjoyable to sniping purists, I find that it just drags out the game and throws weapon balance right out the window, thus making little distinction between the damage your primary sniper rifle does and what a pistol does. In fact, in realistic mode I would simply mark my targets then take them out with a silenced pistol instead, which you can't do on on the second-hardest difficulty since the pistol will take 3 bullets to kill and the first hit will alert the enemy to your presence.