Giving you both a great singleplayer and multiplayer experience, this has to be one of my favorite shooters.
One of the things CoD has always been known for the constant cinematic feel to the singleplayer. Things are defiantly no different here, with some sequences in the singleplayer just blowing you away for the first play-through. While it's a nuke going off right in front of your eyes or escaping from a sinking ship, some parts just feel like a movie. The arcade mode that gets unlocked after completing the singleplayer experience adds quite a bit of life to the game. I played some missions (especially the bonus) mission over and over again just seeing what score I could get.
However, what I really like about the game is simply how it feels to play it. The game is interesting because you can aim down the sights but unlike other games that do this; CoD focuses on this aspect and does it well. You will be able to shoot down enemies close by in front of you from the hip using the crosshair but if the target is even at medium range, you might want to consider the sights and all the weapons have a pretty good distinct feel to them. CoD4 like CoD2 has taken its gameplay formula quite a bit from Halo, where your health auto-regenerates quickly and melee or grenade attacks are easily accessible. A lot of people complain about dieing from grenades quite often and although once you're used to it, it's hardly a problem in singleplayer; it can be a huge pain in multiplayer where grenades can get cooked (held onto so the timer's shorter when thrown). The grenade indicator should have had a larger radius where it slowly gets transparent as you move away from the grenade and more solid when you're near it. This way, you would know how close the grenade is instead of running and then a grenade indictor pops up for a split second and you die in an instant.
Multiplayer is defiantly cool and where I've blown most of my hours of the game into (around level 50 as of now). It is really well done and the perks are defiantly a fun addition to the game. I can tell that they tried balancing most perks and weapons but not all of them are all that balanced. For example eavesdropping is practically entirely useless on the PC where no one actually uses the in-game voice chat for strategy. I find with the first tier of perks I just use bandolier (more ammo) or frag x3 (more frag grenades). The rank (xp) system is really cool and I love how it shows you different challenges (think of them as achievements on the xbox 360 but for multiplayer) and how many total kills/deaths/headshots etc you've gotten. Weapons, attachments for weapons (different sights and grips), camouflage for weapons and perks can be unlocked as you gain more xp which is cool. There are still enough useful weapons you can get in the beginning in the game and getting to level 10 is very easy.
That is to say multiplayer isn't perfect. There's no filter for hardcore servers (meaning you can't really distinguish between hardcore and non-hardcore servers that well even with all the updates they've included on the PC), the grenade spamming can become a problem at a few points, and not all the maps are that great. The biggest problem in my opinion though, is the spawning. You can only spawn (unless everyone's dead where you will randomly spawn) next to your teammate. In other words, if there's a horde of your teammates in one spot, you will spawn right next to them. This sounds good at first but in reality causes problems. If your team is getting spawn killed, then they will continue to get spawn killed because everyone will continue spawning next to each other. You can also spawn right next to your teammate who is getting sneaked up by an enemy you will target you right after he kills him.
The gameplay modes are somewhat on the shorter side and I'm not a fan of the sabotage or search and destroy modes and find that I just play free for all, team deathmatch and domination. Also, there aren't that many maps that I "love" unlike other multiplayer games that I play where they're at least one or two maps that I really enjoy. I'm not a fan of the sniper maps and some of them have a "oh just another map" feeling to them, although some I do enjoy more so than others (but this is more of a personal opinion).
Overall this is probably my favourite Call of Duty game so far and that's saying a lot considering how much I enjoyed the second one. The graphics look great even on low settings and scale very well for the PC which is rare in today's multi-platform games. The sounds and music are right on and fit the game well. The singleplayer is a blast and despite some minor downfalls in the multiplayer, it still eats up your time. The move to WWII to modern times has defiantly been a smooth transition and this is still the same great Call of Duty game from the past.