I don't know if it's just the aiming is chore, or the same line said over and over by the helghast... but this game royally sucks. It's easy to see the evolution or the SLOW evolution of FPS playing the Killzone Trilogy.
I can't recommend this to anyone, the game is stretched in a ton of different directions. The only thing you really know is that you go the only way you can on every map and kill things until it lets you on the next map.
That's all you really need to know about this game. It isn't different, it's nothing special, it's almost an indie game for ps1 that got released on ps2.
Don't waste your time.