In general good game and well worth it.
Starting off with single-player, Campaign unfortunately suffers (as have almost all Cods) from being short, I managed to get through it on veteran in approx. 6 hours. However it isnt an easy game and out of the 3 people in my sort of group at school who play this game I am the only one who has completed it all on veteran (note still neither of them have done it by now and I did it on first day...). You will find some elements difficult in particular holding out in a house against Makarov's goons in the later stages of the game. The campaign does offer a rather strange angle of things, Makarov turns out not to be the major villain and one or two things did make me go "wtf?" and also the ending kind of pissed me off and did'nt strike a chord with me like Cod4's did (I'm sorry I will try and keep Cod 4 out of this but when you have a predecessor like that its difficult). Just a note to end the singleplayer section, the terrorist sequence in "No Russian" did have a lot of hype but really added a gory context to the game (is it sadistic to say I found it fun?)
Now the Multiplayer, Obviously the most attracting feature about the Cod's has been the incredible Multiplayer and this game is no exception. You will have a lot of OMG moments in it (I certainly have) and because of all the new additions etc. the number of noobtubers has decreased however I still think that the LMG is too powerful notably the RPD and M240 but this problem just will never get corrected and it is something that is present in other games (BFBC2 here pisses me off in the extreme f**king medics), and the SMGs seem to have been done down a bit since their incredible powers in Cod WaW (PPSH-41 incredible fire rate + box magazine meant no chance...) so you dont see many out there, I am one of those few and it is nearly upsetting to see one group of weapons sooooo rarely used. A point on the new secondary slot, getting rid of "overkill" they have now allowed you to put a selection of weapons in secondary slot you can keep a sidearm like in the first game or go for a shotgun, rocket launcher or machine pistol. unfortunately I dislike this because everyone sticks a shotgun in secondary slot (even I do for my sniper class and I try not to follow the trend) and it is incredibly annoying to fight in CQB or CQC and have been fighting a noob with an LMG who just pulls out an AA-12 (THE MOST ANNOYING GUN EVER! its a rapid fire shotgun...) and just sprays everywhere and then you have the problem with the Model 1887 the ultimate noob weapon (bling pro, akimbo + FMJ means you have medium range with a bloody shotgun). If they havent used a shotgun for their secondary they are using the tubers which just piss me off (other than the stinger because its fair enough being willing to sacrifice your second slot as a support weapon to kick the ass of whoever is ripping your team apart with a pave low) the machine pistols you don't run into as much but they are still bloody effective and a chance for a non-noob to prove his worth (personally I pick G18 akimbo and .44 magnum akimbo for secondary weapons they just kick ass with steady aim try them yourself). Other than that I only have one real issue, why did they get rid of some of the best guns from Cod4? and why have they messed with the unlock system? Why do you unlock the Ak-47 (the most easy to get and oldest gun in cod4) at the last level?! I loved the G3, G36C, MP5, M1911 .45, W12000 and the Dragunov and they arent in it? it just annoyed me (put it this way those weapons make up all slots apart from one on my PC Cod4 version and thats the M4 carbine which has been changed to be clunky and inefficient in mw2). However must hand it to them some of the weapons they have introduced do kick ass (personally loving the M16, FAL and MP5K). All around (despite one or 2 nagging attributes) it is good, you get used to the new system quickly and though it changes your game slightly from the previous games it doesnt make it unrecognisable, the amount of maps is good (one of the most pissy things about its rival BFBC2 which I have also reviewed is that it lacks maps, MW2 has double BF has and more game modes) and the killstreak and callsigns make it much more tailored to your type of play (if you aren't the greatest player at the game you can use predator missiles etc. if you are elite and often get 10+ killstreaks enjoy some pavelows, ac-130s etc, and the callsigns are quite cool).
Enough on multiplayer XD, Now there is one other mode brought in don't really know why some people said it was like Nazi zombies because it isnt at all... Quite simply it is where you team up with a mate and fight through missions involving anything from doing the snowmobile race from the campaign to holding off the Russians in a sort of survival mode in a sniper's spot. This has been knocked but I found it pretty thrilling on Veteran difficulty only annoying things are the juggernaughts (completely ruin the mission snatch and grab in my opinion) and the fact that the person you play with HAS to be your mate, now I wanted the star 69 trophy (and got it within a few days of getting on spec ops) and it does help to have a buddy play because it allows you to recover when you cock up rather than have to restart entire mission again and btw above I mean on your friend's list, because my PS3 friends from school either didn't have the game, hated spec ops or weren't as keen on getting star 69 as me I ended up having to look for someone in the same position over the internet... Luckily I found a guy who was good at the game and we completed the harder spec ops missions within 2 days. I did manage to do the earlier ones single player and did all of them apart from snatch and grab up till delta by myself (found it much more challenging and brutal XD) so it wasn't SOOOO difficult that you can't do it without a mate at the early stages but once you get to delta or certainly Echo (I could only do the first one on Echo by myself and I did it sooooo carefully it took 11 minutes XD) you will find yourself in deep trouble trying to do it. Nevertheless I do believe it adds a great element to the game but would have preferred if they had a system where you selected difficulty and map and then did a search for a lobby where someone else was also intending to do it like there was for the Co-op in Cod WaW.
In the end the game is fantastic I love the gameplay, some of the new weapons the new killstreak system and additions to multiplayer make it very fun and the spec ops mode is a blast, but Im sorry I must agree with one of the statements at the top, it's not as good as Cod 4... I still play Cod4 more on my PC than I play Mw2 on my PS3 (despite the fact Im level 66 on it and have completed it 100% and got the platinum for it) and I do prefer the storyline of Cod4 compared to MW2 but it is still a very good game and as said in deck worth it. As for its rival BFBC2 I have recently been playing that a lot and it really has changed my opinion of it, large sprawling maps, vehicles, destruction 2.0 engine and squad work does make it in my opinion better than MW2 which last time I played it was showing me what Cod is coming to with no originality just same gameplay with one or two tweaks. Nevertheless got to hand it to them still a good game but DLC is a rip off