I don't see why so many people bashed this game.
The controls are pretty hard to attach yourself to, I adjusted fine when I switched the Sprint and Use buttons around, making the game much much better for me. Keep in mind that this game will put a lot of wear into your dual shock controller, the main story/campaign alone took me 30+ hours to complete, and I spent another 5+ hours with the Battlefield/Multiplayer options. The Battlefield is what will keep you playing this game for a while, even after you've finished the main story/campaign, the Battlefield has enough options to keep anyone busy, but it has its flaws, like character selection, just choose your side, Helghast or ISA, nothing beyond those two, just one character for each force.
Although there is another character aspect that will keep you playing. The character selection for the main game, you can play as one of the four main characters in most of the missions, you meet each character as you progress through the game, with the addition of each character you will find your favorite and the most functional to your liking.
For a FPS, especially on a console, this game is really difficult at first, on Easy, the game will get you frustrated, as it is no easy, fly by night, game. Playing the game on Normal or Hard will thus proove your skills with this game, and especially if your a completist such as me, but once you've gotten a hold on the controls and AI tendency this game will become very easy unfortunatly.
Overall, Killzone isn't a perfect game by any means, but it surly isn't a bad one either, if you give this game a chance tweaking it a bit and stop thinking about other games you will enjoy this game for what positives it does have.