Basically; Killzone 2 is a great game, with an even greater multiplayer, you do NOT want to miss out on this game!
The Multiplayer is the BEST part about the killzone universe in my opinion, with up to 32 players in a match, many diversified classes to mix and match, and a ton of rewards or "ribbons" to collect in-game, you'll always be playing differently, I know I am. One issue people always complain about in multiplayer is that the classes are "unbalanced" such as assault, because they get rocket launchers. I completely disagree. Although rocket launchers may be be a one hit kill, and are like grenades that fly in a straight line, they have the disadvantage the same number of times you do to them. Assault classes only get 3 rockets per life, which is very easy to use up, and easy to end up killing yourself with, so no matter what you'll be just as balanced a class as anyone else on the map.
Speaking of maps, they are very well detailed. From the wall textures, to the large C4 explosions, even down to the shredded flags waving in the wind on specific buildings. Each map has a different mood and is set up in such a way as to give each team an equal amount of disadvantages and advantages in all the mission types. All of which are fun; such as planting or defending a bomb in either side of the map, Capturing bases for your team, assassinating an enemy, or even the plain old "kill everyone in sight" game mode. However, the "auto-select team" feature can sometimes work for or against you by putting all the good players on one side, and bad players the other. Nevertheless, it is still addicting and never gets old or tiring.
Last but not least is the trophy system, which is VERY well set up. There are trophies for newbies, and for FPS veterans. You can earn trophies for beating levels, killing a number of enemies, performing specific in-game feats, obtaining ribbons (as mentioned previously), and even for being in the top percentage of players for that week.
Overall, this is a GREAT game, and I would reccommend it to anyone; it's hours and hours of replayable entertainment for anyone, and if after all this you're still on the fence about this game, let me just tell you that this is one of my personal favorite games, and is nonstop fun everytime you pop this game into your PS3. I don't care who you are, or what your interests are; you WILL love this game!!!