If you liked the first game, buy this right after you've read this review or better yet... why wait??? If you just like games which involve action, stealth, and a Hollywood style plot go for this.
The level of realism in this is phenomenal, if you take some time to look at the DVD Video that comes with MGS2 you'll find out exactly why the this game is so militarily accurate when, for example, if you're trying to hide from the enemy in a locker while they're searching the room you're in they'll be perfectly coordinated, the closer they get, the more your heart begins to fill out the silence and the Dual Shock vibrates.
Then there are the small touches, such as, have you ever noticed in Bond films that when James is in a gunfight, he always holds his gun UP? It's also explained that this is militarily incorrect, therefore if you push yourself against a wall, a manoever which will be perfectly familiar to those who've played the first game, you'll notice that both Snake and Raiden hold their guns down. Then try doing the same thing on the first game; do you see the difference???
The big snag for hardcore Solid Snake fans is that he is not playable throughout the majority of the game. Instead, you'll have to control Raiden. When you take a look at the quality of the game overall, you should be able to look past this with ease.
This game was made to be much like a Hollywood action film, with it's enormous usage of FMV and Codec scenes designed to progress through the story. Therefore, the first time you play this you will have to be prepared to sit through a lot of dialogue between the different characters.
But, all in all, if you appreciate a decent game, buy this and you won't regret it.