Serious Sam 3 is probably the weakest SS game I've played so far. It can be fun at times but Croteam have gone completely backwards with the gameplay. Serious Sam 2 fixed a lot of the problems with the gameplay but SS3 seems to add problems that weren't necessary in the first place.
For starters, this was the Serious Sam game that added in reloading and iron sights for some weapons. The Deagle is fine with these as it has infinite ammo and the Colts in the classic games also needed to be reloaded, however these military FPS features apply to the Assault Rifle as well. The Assault Rifle replaces the Tommy Gun and anyone who has played a SS game will know you use the Tommy Gun a lot. Having to reload every 40 shots and having to aim down iron sights just for better accuracy does not fit into the gameplay loop at all. When you got Bio-Mechanoids firing rockets at you from every angle alongside a horde of Kleers and Werebulls you need to strafe past, you don't have time to reload. Even the regular shotgun needs to be reloaded which is even more of an annoyance.
Speaking of weapons, the Sniper Rifle and Lasergun, which are staples to Sam's arsenal, are rarely used at all and are only found as secrets. Not only that is you get little to no ammo for them. Both guns were some of the most important weapons in previous games but in SS3 they are incredibly hard to find and are very limited in their use.
SS3 also added in plenty of new enemies. However, they also added a more obnoxious enemy type than the Kleers, that being the Witch-Brides. If they have line of sight of the player, they will slow you to a crawl, lift you up and start damaging you, making yourself an easy target to the 5 million other enemies around you. They can also only be damaged when they're charging up their attack and will teleport away when you damage them enough. As a result, fighting these enemies are such a chore. SS3's enemy line-up also suffers from having just far too many hitscanners. The many hitscanners include Cloned Soldiers (which blend into the environment too often), Technopolyps, Adult Arachnoids and Hatchling Arachnoids. These enemies are used so often that you need to take cover and hold the line, which is against what Serious Sam has always been about.
The colourful and diverse levels are gone from SS2 as SS3 uses the same generic copy-pasted city ruin maps that someone out of the loop could mistaken for as a Call of Duty map. Unsurprisingly these levels are recycled from a military shooter that Croteam scrapped, so they just used them here. Some levels also introduce these horrible underground segments where your vision is limited to a flashlight and you actually move slower. They also introduce these annoying monkey enemies that will always hide from you and attack at random and once again, they are a complete chore to fight against.
The final boss is easily the worst boss I'd had to fight in the series. The boss regenerates health and you cannot out-damage his healing. What you're supposed to do is throw these metal spikes laying around the map on his back and to do that you need a jetpack. The game doesn't tell you this outright but because I'm the only person that reads the Netricsa entries I knew that I had to throw these spikes at the boss' back. But the game doesn't tell you how to get there. I spent most of my deaths on the fight trying to find a jetpack or a flight powerup, which I did eventually and then the game spawns in a lot of high tier enemies. This is also the first time you use the jetpack, so you have to get used to the wonky flight controls alongside the unnecessary overheating gimmick in the middle of this huge final boss fight. The fight takes so long as the boss will never turn his back to you until the Sandwhale attacks him, which just seemingly happens at random. You do this a couple times until he gets stunned long enough for you to kill him. It sounds easier said than done.
Overall, SS3 is a definite low point in the series where Croteam tried to be "legitimately serious" and "realistic" when the best SS games are the ones that aren't serious at all. There are a few good points such the soundtrack, new weapons like the C4 and Devastator and some of the combat encounters. But the game suffers more from trying to mash together modern military FPS features in a fast-paced boomer shooter (which most boomer/retro shooters tried to do during the early 2010s) alongside uninspired locations and terrible pacing. I can't rate SS3 more than 3 stars.
For starters, this was the Serious Sam game that added in reloading and iron sights for some weapons. The Deagle is fine with these as it has infinite ammo and the Colts in the classic games also needed to be reloaded, however these military FPS features apply to the Assault Rifle as well. The Assault Rifle replaces the Tommy Gun and anyone who has played a SS game will know you use the Tommy Gun a lot. Having to reload every 40 shots and having to aim down iron sights just for better accuracy does not fit into the gameplay loop at all. When you got Bio-Mechanoids firing rockets at you from every angle alongside a horde of Kleers and Werebulls you need to strafe past, you don't have time to reload. Even the regular shotgun needs to be reloaded which is even more of an annoyance.
Speaking of weapons, the Sniper Rifle and Lasergun, which are staples to Sam's arsenal, are rarely used at all and are only found as secrets. Not only that is you get little to no ammo for them. Both guns were some of the most important weapons in previous games but in SS3 they are incredibly hard to find and are very limited in their use.
SS3 also added in plenty of new enemies. However, they also added a more obnoxious enemy type than the Kleers, that being the Witch-Brides. If they have line of sight of the player, they will slow you to a crawl, lift you up and start damaging you, making yourself an easy target to the 5 million other enemies around you. They can also only be damaged when they're charging up their attack and will teleport away when you damage them enough. As a result, fighting these enemies are such a chore. SS3's enemy line-up also suffers from having just far too many hitscanners. The many hitscanners include Cloned Soldiers (which blend into the environment too often), Technopolyps, Adult Arachnoids and Hatchling Arachnoids. These enemies are used so often that you need to take cover and hold the line, which is against what Serious Sam has always been about.
The colourful and diverse levels are gone from SS2 as SS3 uses the same generic copy-pasted city ruin maps that someone out of the loop could mistaken for as a Call of Duty map. Unsurprisingly these levels are recycled from a military shooter that Croteam scrapped, so they just used them here. Some levels also introduce these horrible underground segments where your vision is limited to a flashlight and you actually move slower. They also introduce these annoying monkey enemies that will always hide from you and attack at random and once again, they are a complete chore to fight against.
The final boss is easily the worst boss I'd had to fight in the series. The boss regenerates health and you cannot out-damage his healing. What you're supposed to do is throw these metal spikes laying around the map on his back and to do that you need a jetpack. The game doesn't tell you this outright but because I'm the only person that reads the Netricsa entries I knew that I had to throw these spikes at the boss' back. But the game doesn't tell you how to get there. I spent most of my deaths on the fight trying to find a jetpack or a flight powerup, which I did eventually and then the game spawns in a lot of high tier enemies. This is also the first time you use the jetpack, so you have to get used to the wonky flight controls alongside the unnecessary overheating gimmick in the middle of this huge final boss fight. The fight takes so long as the boss will never turn his back to you until the Sandwhale attacks him, which just seemingly happens at random. You do this a couple times until he gets stunned long enough for you to kill him. It sounds easier said than done.
Overall, SS3 is a definite low point in the series where Croteam tried to be "legitimately serious" and "realistic" when the best SS games are the ones that aren't serious at all. There are a few good points such the soundtrack, new weapons like the C4 and Devastator and some of the combat encounters. But the game suffers more from trying to mash together modern military FPS features in a fast-paced boomer shooter (which most boomer/retro shooters tried to do during the early 2010s) alongside uninspired locations and terrible pacing. I can't rate SS3 more than 3 stars.