Killzone is a decent shooter. Unfortunately, the game is also a severe underachiever and could've been so much better.
First off, I wanna comment on the storytelling. EXCELLENT. I honestly think Killzone could make an entertaining movie given its excellent cinematic storytelling. The cutscenes are VERY well done. Music composition is excellent for the tone of the scenes, the acting is good, the dialogue great, and I just remember thinking to myself multiple times while watching cutscenes how much i'd like to just sit there and watch continuing scenes like those for the rest of the story as a movie. The cinematics/storytelling is Killzone at its best.
The gameplay is where the game's potential is restricted. The A/V is great. Killzone boasts some great visuals given the hardware and I can tell from some of its visual hiccups that its a result of the PS2 limitations and could've been even better on the Xbox. The audio is great, too. All of the weapon sound effects are amazing and immersive. Just the sound of the game reminded me of the seemingly endless action in Black Hawk Down.
Now A/V aside, this is the main thing that boggs down the gameplay...the gameplay. Simply put, with the exception of a few scripted events, its pretty dull, and the reason is because it feels very repetitive and there is little excitement in between those scripted events excepted above. After a while, you really just start getting tired of walking along a path, kill some soldiers, continue on, kill some more, continue on, kill some more, continue, and kill some more. You may say thats how all FPSs are in effect, I know. But the fact is, Killzone pulls this off in a way that you really notice the repetition and get tired of it because the pattern drags on throughout lengthy. A major contributor to this feeling is the fact that the vocal clips from the Helghast Soldiers are obviously all voiced by the same 1 or 2 people and there is a severe lack a variety in the things they say beyond the scripted events. By the time you finish the first level, you've probably heard all you're going to hear from your enemies for the rest of the game. Their dialogue gets old and repetitive very fast.
The inclusion of permanent combat comrades in the gameplay is a nice touch, however, i'm annoyed by the fact you may end up feeling like you're "babysitting" their actions. They typically remain behind and only move when you move. If you get aggressive, they follow suit, but also if you run back and take cover, they follow you. You could be pinned down somewhere, taking cover to recover your energy, and there are you 3 comrades who CANNOT die sitting there right behind you doing absolutely nothing when they could be up ahead fighting while you heal your wounds. I realize this was probably done intention for the purposes of not letting the player make the A.I. do everything for him/her, but at the same time, it kinda takes out the point and fun of having comrades alongside you if it doesn't feel like they're thinking for themselves.
I think what is largely missing from the gameplay that could've made it a lot more exciting is gameplay music selection, a la Halo. Beyond the cinematics you will hear no music and I really think the gameplay has a lot to gain from some music to set moods and pump up the firefights. Given the quality of the music in the cutscenes, I think in-game music could've been pulled off well. Its a shame it wasn't implemented.
Overall I found Killzone to be a decent shooter worth experience. Its certainly not a bad FPS, its just a severe underachiever in terms of how good it could've been. If Guerilla can capitalize on their gameplay shortcomings, and continue to do what they did right, then I think Killzone 2 can be an awesome game.