It's easy to slam Kane and Lynch 2 because of it's rough history. As such those who already know it or just want to see how this game stands on it's own can skip the next paragraph. I should also mention I played this game in co-op and on PC.
The whole thing started with Freedom Fighters. An underrated classic of a game on the PS2 where you led a squad of rebals in an occupied US. The game hinted at a sequel. Then on Xbox360, rather then a direct follow up they made a spiritual successor called Kane and Lynch, a game that had many good ideas but suffered from being bloody awful. Famously Jeff Gurstmann got fired from gamespot when he gave the game a fairly negative review despite the games heavy advertisment on the site.
Kane and Lynch 2 plays out in a 24 hour story as the titular characters turn up for an arms deal. Of course, things don't go according to plan and you have to shoot you way through waves of badguys, or bad-er-guys, whatever. Dude be needing shot. For what it's worth, the set up is kind of nice. The people look ugly like, you know, real people rather then steriod abusing super models, and when combined with the gritty, handheld camera, fly-on-the-wall feel of the game makes the game feel tough and savage, at least at first. Unfortunatly this is also when the game is least fun as the guns are inaccurate and lack punch.
As you progress the game gets better as the enemies weapons, and therefor the weapons you can swipe, improve. The game becomes a fun cover based shooter with enemies that flank you and generally give you a hard time, or it could be that they were spawning behind us. Either way there was alot of "Where am I getting shot from?" and "I'll cover this side." throughout the game.
The game is fun enough, and in my opinion better then Gears of War as far as third person co-op shooters go, even if it does get formulaic with the same paturn of "Sneak past these unavoidable guys, they see you, wave of guys, co-op door, repeat". If you are wondering, there are some cases they litterally never turn away from you or won't move from a door you have to progress through.
As the game goes on, it starts to lose it's edge. As you play, chinese gangsters change to cops, to army men, and at this point the game loses most of it's gritty feel. All you need is a couple of a skull masks and you could be playing Army of Two. Not really a problem, but it is a bit of a shame.
However, the game's biggest crime, the thing about it that really wound me up was the ending, or rather the lack of ending. The game doesn't end. It just stops. No boss fight, no climactic battle, no closure. It's not really spoilers to say, but skip ahead if you really must. The ending has you fighting your way towards a plane, and when you reach the plane the character start running up the steps, still under fire, cut to black, credits roll with some Jpop love song and no epiloge. What the hell? At first I thought it was a glitch or we skipped it, but no. That's exactly how it happens.
So, the important part. Is it any good? Well, ignoring the unique look and feel, it is a competant co-op shooter, and fun with a friend. It might be worth your time, but not your money. It's worth getting on sale if you have some spare cash. However, if 'fun enough', 'okay' or 'fairly decent' isn't good enough for you, I say stick to Halo or Mordern Warfare 2.