The users that gave low scores simply did not understand this game
I've played through the game with just a knife, and i've also played through like Rambo, both were a lot of fun! Each level gets harder as you progress, allowing for deeper and more complex sneaking tactics to take out the target. You can of course still blast through the game with a machine gun.
Ammo is quite sparse, and you really get the feeling that you are all on your own to finish the job.
You get points for not spending too much money on ammo and guns. You also lose points for killing civilians and unncessary people, but you dontl oose the game! There is actually a suprisingly deep storyline, which is mysterious and open ended but involving.
The graphics are amazing, they still look immersive today (2011)
The game looses some points for being a little heavy on the 'trial-and-error', but I think it was amazing nevertheless.
The bottom line is, if you want to be spoonfed a challenge, this game isn't for you. If you like figuring out puzzles, learning from your mistakes, strategically planning out your attacks - this game is for you, and my favorite in the series!