Killzone did have some technical problems (which the developers claimed were solvable with a few more months of work), but beyond that I suspect that the game introduced a true innovation to the FPS genre. Typically, the camera does not move from the FPS perspective, but in Killzone, the camera moves when drawing weapons (camera movement is different for each weapon, with none for the pistol), throwing grenades, reloading, and even shakes uncontrollably when too near a blast. I found that this significantly enhanced the immersion of the experience, and I hope that more games will start doing this.
This Youtube video shows a little of what I'm talking about:
http://www.youtube.com/watch?v=fZzYTO0RCG0&mode=related&search=
I do not know how many other FPS's have sprinting, but in Killzone, sprinting is important when moving between cover. You cannot fire while sprinting, you can only sprint for short periods, and when done sprinting there is a delay before you are able to shoot again. This adds depth to the gameplay, and makes for a more intense play experience.
Different weapons also obscure your view to varying degrees, so it can be a disadvantage to run around with the multiple rocket launcher when you can't see what is to your right side.
The weapons themselves are well balanced each requiring different tactics- some are only good for short range, while others only work for medium range. The ISA assault rifle is very good medium-range weapon because of the grenade launcher, while the Helghast rifle is excellent at short-range because of the shotgun shell it can fire. One of the game designers is supposedly really into weapons- flying all the way to Vegas to shoot guns. I too shoot weapons (I hunt), so I appreciate the extra care that has gone into creating depth in the weapon experience.
Killzone's art design is some of the best that I've ever seen in a game. Many of the locations appear to be functional- a space port, apartment dwellings, research facility, etc. The concrete textures show incredible attention to detail.
If you get a chance to play the game, be sure to play around with the Battlefield mode, and try out some challenging scenarios where you are outnumbered, or have a very limited amount of time to accomplish something.
Guerilla Games has shown that they are very talented, and I wait in anticipation of their next opus.
