If you liked the previous games, you wil really enjoy this title!
The storyline is the best of all in my opinion. Of course it is about the threat of several nuclear weapons and such like in all titles, with even a 1964 version of the Metal gear weapon. It teaches you a lot about the cold war and it always stays understandable, not like the ending of Mgs: 2, wich was disappointing in my opinion, didn't made sense at all. The only thing I don't get is this; It's 1964, and already guards have portable walkytalkies, snake has thermal goggles, nano communication..? I'm not saying they shouldn't added those things in the game, just that it seems a little futuristic (also the Metal gear seems way ahead of it's time).
The graphics are very good for the PS2, the Metal gear solid games have better graphics as most of the PS2 titles. Thow the leaves sometimes are a bit blocky, who cares.. characters look awesome, snake most of all.
I classified this game innovative, cause the fighting with camouflage in the jungle in a stealth game is a rarity, and don't forget the animals! go get this game if you liked the series. You will have a blast of playing and 'watching' this game. If you are a bit impatient, or just no fan of stealth games, go rent it or borrow it at first or something.