This game nails the FPS concept so well, it should be illegal.
AS FOR THE POSITIVE POINTS:
1. Offline co-op. I had plenty of fun playing the game with my buddy. Only thing is that I'd like to have the ability to have a horizontal split screen option as well.
2. The controls are MUCH better in contrast to my expectations. I am already waiting for my XFPS to come in but I was surprised at how fluid the controls are. The analog sensitivity is perhaps 30% higher now than in the second game. Which almost feels like a mouse to me, since I am a PC gamer at heart.
3.An even more advanced AI. The second game without a doubt had the most advanced AI in the world. The third game made the AI even smarter. They still retreat when their line is broken, they cover each others' retreat, they still throw grenades. Now, they throw even more grenades, they have more advanced weapons than you, they can roll out of the cover in prone position, shoot you and then roll back in.
4. The best looking visuals on PS3 perhaps after the Uncharted 2. The PS 3 really reinvented the wheel on this one and once again displayed what PS3 still can do despite it being an outdated system in my opinion (as all consoles are). This game displays volumetric smoke, realistic damage to buildings and objects, advanced physics, advanced everything.
5. Engaging story with some twists as well as insane cut scenes that are not as overblown as in COD series, but are believable enough to amaze (except for a few incredible parts where your allies survive unrealistic explosions and falls).
6. The cover ability. Now THIS is what the cover system should be like in all shooters. I could never get past the point where you take cover and then you are magically able to see what is going on all around you without you having to take a peek. For me, that just makes the gameplay unrealistic. So as far as I know, only 3 games nailed this cover system where you actually have to peek out of your cover to see what's going on: Killzone 2, Killzone 3 and Rainbow Six Vegas 2 (multiplayer versus mode).
7.The ability to slightly slide as well as see your legs in regular mode. This is a big one for me. The ability to see my legs in the FPS as well as actually cast a shadow is a feat of very very few FPS games for some reason.
8. Plenty of content. The game occupies 41GB of space on the blu ray disk. The maps are huge and there are plenty of things going on on the screen.
9. The ability to flank your enemies in most situations just like in the second game.
10. Satisfying firefights and feelings of satisfaction every time you kill a Helghast. You actually feel the achievement of having killed an enemy because they aren't easy to kill as in COD series, etc. Here you actually have to outsmart your enemy every time you engage.
11. Satisfying close-quarter kills.
12. The sound is on par with Battlefield 2: BC. Enough said. The voice acting and lip sync is also top notch.
13. No more collecting intel cases and no more shooting at propaganda signs. I am glad I didn't have to be distracted by those things as I was in the second game. Incidentally though, there are twice as many trophies to earn in the second game than in the third one.
14. Deep multiplayer. The amount of ways in which you can play in the multiplayer mode varied and insanely advanced. The hard earned skill points are spent on upgrading your abilities and unlocking weapons whatever class you play as. The maps are also pretty big. The maps have their own cut scenes and sequence of events you have to follow in order to either defend or attack your objectives - I've never seen anything like that before.
15. The game utilizes the havoc engine, I love it.
THE NOT SO POSITIVE POINTS:
1. Plentiful of ammo this time around and the ability to have primary, secondary weapon as well as pistol (which is useless in the third game). This means that you can blast away more ammo without having to conserve (like in the second game) and you will constantly see ammo boxes that will refill all of your ammo as well as grenades. I almost beat the game twice (second time on the elite mode) and did not find it as hard as the second game simply because I could grenade the enemy into the oblivion. The pistols are useless in this game.
2. If you aren't playing co-op, Rico is not as likely to revive you as he was in the second game for some reason.
3. I am a bid divided on the jet pack. Don't get me wrong, it's innovative and very few games if any had implemented it fully; but it caused me plenty of frustration in single-player mode.
4. I still do not feel like I play as the good guys here. I didn't play the first killzone, but from what I've learned, the Helghast nation is always the one on the defensive except for the third game where they counter-attack with full secretly hidden force. They are sorta a mix of Nazis and Commies but the extremely oppressed ones. I might be wrong about this but I still felt like I was the aggressor and the invader of the human colony that wanted independence after being oppressed and after having to rebuild the entire planet from scratch after the initial wars. But maybe that's the beauty of this game. You don't have to be the good guy as in 95% of games.
AS FOR THE NEGATIVE POINTS:
1. Infinite ammo for the pistol - again. (unrealistic)
2. Chase sequences - not my thing, but at least they don't last as long and they don't become frustrating.
3. No on-line co-op.
4. Reloading your checkpoints gives you most of your depleted ammo back if not most of it. I sorta see this as an exploit.
In the end, if you are a PS3 owner, you will still most likely play this game at some point in your lifetime. I was always slightly reserved about Killzone 2 because I wanted to play in on my PC with better graphics, anti-aliasing and controls. After I played the third game, I realize that PlayStation 3 deserves this exclusive fully.