There are two big reasons to play this game. One: the jungle. Two: the characters.
The story is set in Russia, 1964. Snake is a CIA agent trying to extradite a weapons scientist to the US. Sounds simple enough. There are a few bumps and twists along the way of course, but compared to the previous games the plot is fairly straightforward. I think it's rather boring. It's mostly irrelevant though; unlike Sons of Liberty, this is not a game that is held up (or destroyed, depending on your perspective) by its story. It mostly stays out of the way and allows the more interesting parts of the game to shine.
The characters, for example. Different from most video game characters, they are not paper thin. You're never quite sure what the motivation for their actions is. Even dependable bad-ass Snake has some questions raised about his motivations. However, it's not overdone, as it easily could have been. The sides are established early on and for the most part everyone sticks to their own. It's just the question of why they are where they are that keeps you involved. Instead of wanting to see what they'll do next, you want to know why they've done what they've done. The downside to this is that when you do discover the answers, it's a little anticlimactic.
The characters that you only speak to over your radio are not so fleshed out. Their purpose is to provide information and a little extra humor. They do this well, but you'll probably forget they exist for long stretches of the game.
You won't forget the jungle. If you've been paying attention to the media, you've probably seen a lot of jungle. The jungle is pretty great. The vegetation is lush and thick; and there's a wide variety of wildlife roaming about. It seems like a living place more than any other location in the game. And yes, there is more to it than jungle. There are caves, a mountainside, and a big military base. These places are nice, and definitely necessary in the interest of variety, but they feel empty compared to the jungle.
Some of this empty feeling has to do with the gameplay mechanics. There is no radar; at least not like what you're used to if you've played the previous games. In the jungle, this successfully adds to the survivalist feeling. But in the military base, combined with the camera angles, well... it's just annoying mostly. Unless you want to get in a big battle you have to be constantly stopping and switching to first person view to look around for guards. Now, I'm not in support of a first person control mode or even a free control camera in MGS. Either option would totally eliminate the cinematic feeling that the games portray so well. Really, the only reasonable solution I can think of would be to just give you the radar back as you enter the base; but that would make the lack of radar in the jungle seem like a bigger contrivance. Not to mention that the technology would be impossible in 1964, and the game generally tries to stay semi-realistic in that respect.
Anyway, to get back to my point: the non-jungle locations feel empty because you just can't see very much at once. The camera is at such an angle that you can only see your immediate area, and naturally the layout of objects on a base or mountainside is not very dense. The solution to this problem? I have no idea. Perhaps a lower and closer angle camera would be better, but that could also feel too gamey and not cinematic.
The lack of radar isn't the only thing that makes the jungle feel like a test of your survival skills. Hunting, eating, healing, and camouflage have been introduced. Selecting camouflage is done from the menu; they give you an index number that tells you which camouflage will make you blend in best. Eating and healing are also done completely through the start menu, which somewhat diminishes the whole survival aspect. It's just a matter of selecting the right things from a list when you need to, any shmuck can do that. Hunting isn't very difficult either, but at least you have to kill/capture your prey. And again, these things feel out of place when you're in the military base. When was the last time you saw an agent sneaking around with a backpack full of meat and ramen noodles? I may be nitpicking now, but when there's a regular amount of frustration; I start to overanalyze everything trying to figure out if I'm doing something wrong.
The gameplay isn't all frustration though. The boss fights are always interesting and each one requires a different strategy. There's also a fun sequence on the sidecar of a motorcycle. And for the most part the "flawed" gameplay mechanics work together in the jungle pretty well. Oh, and I almost forgot the bonus Snake vs. Monkey mode. Snake takes on a bunch of monkeys. That's pretty fun.
Technically, the game is well done all around. The graphics are about as good as the PS2 can do, I think. The music is on par with a Hollywood action movie, which I guess makes sense since the composer of this game--Harry Gregson-Williams--is the composer of many big films. The weapons and ambient noises all sound good; the voice acting is well done. The facial animations and lip syncing seem pretty stiff, but maybe I've been spoiled by Half-Life 2. Still, I remember the hype for the PS2's "emotion engine;" it seems like they should be able to express emotion pretty well... ya know? The rest of the character animation is very good though. Enemy AI is good, but not great. Sometimes you'll notice them doing something stupid, or they'll see you when they probably shouldn't be able to. They mostly do ok, but they should've taken a bigger step up from MGS2, considering the 3 year gap.
I prefer MGS2, overall. It has more fun with itself. Snake Eater has fun too, but mostly near the beginning; then it starts getting more and more straightforward as it winds down. I guess it's a matter of personal taste, but I prefer some nonsense in my gaming. Still, this is a very good game, and it's not too short. My first time through took a little under 20 hours; I may or may not play through again, I'm not sure. I've spent a couple hours on the Snake vs. Monkey mode but it would be nice if there were some more levels since it's such a simple mini-game.
Summary: Good game, but not all of the ideas work as well as they should.
I give it 4 out of 5 magic rainbow-colored top hats.