Subpar story, but amazing in all other aspects.
Person 1: Okay Snake, we need to get Person 2 transported safely in the van or we will fail our mission.
*ten minutes later, after a long arduous struggle, van is destroyed*
Snake: NOOOOO!
Person 1: Don't worry, that wasn't the real Person 2. The real one is on a boat.
Imagine something like that happening thirty more times in the game. There's always a ridiculous, unbelievable explanation tied to every twist. It gets to the point that you yourself explain anything you don't understand with all sorts of strange rationalizations. Remember the first MGS? Or even MGS 3? Both games' stories worked so well because the plot twists were kept to a minimum. The plot BUILT UP to the plot twists, making them both believable and shocking. The same can't be said about MGS 2, but at least that game explored some truly thought-provoking themes and ideas. MGS 4 has interesting themes, but it doesn't bother to explore them thoroughly.
Of course, there are other problems with the story than the plot twists, namely the game's tendency to go into over-exposition. There is no such thing as concise dialog in this game. However, this is a problem that has plagued the MGS series since its inception, and frankly it doesn't bother me at all. Now let's move on to the numerous good things about MGS4.
Instead of diving straight into the gameplay, I would like to discuss the cutscenes first, since they convey the story. The cutscenes make up for the story in spades. They truly are pre-rendered quality, but they aren't pre-rendered at all with perhaps three exceptions. The people in this game look exceptional, and convey emotion more realistically than I've ever seen in a game. In particular, the little girl Sunny is perhaps the most human-like child in the history of video games. She's adorable. Also, Snake's struggle as an old man saddled with the burden of saving the world is conveyed brilliantly, and is genuinely touching. One moment that stood out to me in particular is when Colonel Campbell essentially tells Snake "the fate of the world is in your hands," and Snake looks completely helpless. As much as I dislike the plot of the game, I have to give high praise to Hideo Kojima for making the main character not the typical young Rambo-style super soldier, but a dying old man.
The sound aspect of MGS 4 is perfect. The sound effects are what you would expect from a modern warfare game, and the soundtrack is beautiful.
Finally, the gameplay! Kept you waiting, huh? Well, prepare to do a lot of that in the game, as this is a MGS tradition. The cutscenes are LONG, but they're so pretty you probably won't care (codec conversations have been kept to a bare minimum in this iteration of MGS; no more "let's switch to codec so no one will hear us"). The gameplay has been greatly revamped; it's very similar to western shooters like Gears of War now. Despite this, Metal Gear veterans will be able to get used to the controls quite easily. Those who've never played MGS 2 or 3, and those who don't play shooters will have a much more difficult time getting used to the controls. What else can I say about the gameplay? It's still Metal Gear. It's still about stealth, except now you'll often be sneaking through battles between warring factions, instead of just sneaking through guards. In one act(there are five) you'll even have the opportunity to ally up with a local militia against the PMCs(Private Military Contractors).
Unfortunately, and this has been a problem since MGS 2, what partly kills the "stealth" gameplay is the tranquilizer gun. It's just too good. It isn't so much about sneaking past people than it is about tranquilizing them. It doesn't kill the fun necessarily, but it makes the number of tense situations in the game very few (especially on easy and normal mode), which is a shame. Another gripe I have with the gameplay is that the boss battles are for the most part slightly disappointing. The variety and creative-thinking of boss battles from previous MGS games are not found as much here.
Metal Gear fans, I don't need to tell you that you need to buy this game. To everyone else, make sure you know what you're getting into. It is definitely an unforgettable experience, but it is also an acquired taste