This is basically Modern Warfare with a fresh coat of paint and refreshed multiplayer, and overall that is a good thing.
The single player campaign is what you would expect from just about any FPS. However MW2's campaign lacks length but does include its share of unique gameplay. There are some intense moments but again, this is a FPS so there isn't much else to say. The plot directly follows its predecessor. There are a few new characters you play as, but you don't really get to know much about them throughout the campaign. A few twist and turns, some gunning here and there, some explosions, and about 4-6 hours sums up the campaign really.
So unfortunately the campaign isn't quite satisfying enough to call this an all-out amazing game, but this is why there is the incredible multiplayer the Call of Duty franchise has offered for the past several years. And luckily MW2 takes these same mechanics and takes them even further. Instead of your typical UAV, airstrike, and helicopter, IW has added a butt load of new killstreaks, and even perks, some of which have to be unlocked by leveling. You can use 3 at a time, and overall it can be hard to decide which ones to get. They range from a UAV (3 kills) to a "tactical" nuke (25 kills). Each of the killstreaks are helpful in thier own way, and a select few of them are even quite powerful. Luckily to balance things out you can blast enemy air support out of the sky with such sidearms as the Javelin. This also earns you experience...
As most would realize the online's reward/experience system has drastically improved. There are experience bonuses for things you would normally do in other Call of Duty games such as getting headshots, far ranged kills, shooting down enemy choppers, harriers, etc, and even killing the person that killed you last. It still takes a very long time to prestige, but the rewarding system and level 70 cap really make it feel you are doing a lot. The weapons are somewhat balanced, although to me it feels like assault rifles significantly outclass other weapons. But still a light-machine or sub-machine gun can perform just as well in the right hands. Shotguns have also been made to be secondary weapons which I think is really cool. There are also all kinds of attachments. Returning attachments include silencer, red dot sight, ACOG sight, grip, and basically all the other ones... but there are some new ones like the thermal scope attachment.
Overall I have to give the online multiplayer some props for improving and giving more of a rewarding experience. The graphics seem slightly better in my eyes, but nothing jaw dropping. The sound is amazing as you can hear an explosion from across the map, hear the jet engine of a hovering harrier, and hear bullets flying right over your head. The online can be very fast paced as it was in MW.
Spec. Ops is an new feature in Modern Warfare 2 that unfortunately I havn't played yet. But the fact that they did add something brand new to the game is cool, and whenever I get to playing it I might add my opinion on it in this review.
And that's about it. Modern Warfare 2 is a must have for fans of the previous 2 games (or even just MW for that matter). There are plenty of game modes to choose from in the never ending online universe of Modern Warfare 2.