Chaos Theory on the PS2 is good, but it is not the best version out there.
In Splinter Cell: Chaos Theory, it is in the near future in 2007 (which is now the presesnt). There are tensions between Japan, China and North Korea, and Chinese blockades are set up in the Korea Strait. Japan asks the United States for assistance. The Third Echelon team then gets caught up in an incident with gurella's and Sam Fisher is sent in.
In this game, you must use unique tactics to get through levels and complete objectives. Some are extremely basic but vital to your success, such as crouching, crawling through vents, picking locks, knifing someone, climbing on pipes and rolling. You also have night vision, thermal vision, a pistol and an advanced SC-20K, which has many different attachments. You will also have to do advanced stuff, like hacking, rappeling, jumping on enemies, among other things. There are many moves, and lots of them are a blast to play, but you will find that you will be doing the same things over again.
In this game, you have to be careful about what you choose to do. Shooting is not necessary, as stabbing is quieter and more effective, and you can also get behind someone, grab them, and knock them unconscious. Also, you will have to be careful of alarms. You don't lose after a certain number are set off, but the game does get harder after a lot are set off, so be cautious of what you do. It is also a good idea to hide dead bodies so they don't be seen. Some dead bodies aren't necessary to hide, but it is fun dropping them off a cliff or hiding them in a dark area.
The campaign is indeed a highlight in the game, as it is more open ended than the other games in the series. For example, when you face a door that you need a keycode to open, you have two options, you can either go around the level finding it, or you could try to open the door on the spot by hacking it, but risk setting off an alarm. There are a number of missions with choice to like that.
The co-op is indeed pretty fun, especially at the beginning in Seoul. Basically, the missions aren't very long, but they do challenge you mind by making it hard to complete. For example, in the Streets of Seoul, you will need to open a door, but, there is a guard on the street, as well as a number of guards in the room with the door in it as well as an auto-turret. But after a while, the co-op does seem to lose it, and it feels empty.
The graphical presentation in the PS2 version is not as great as it is in other versions. The game is very dark, sometimes even too dark to look at. But when you put on those night vision goggles, it is still hard to look at. The graphics are no where near the XBOX's amazing visuals.
The audio is good, but exaggerated. For example, walking on gravel, except if you have a gun out, is very noisy, and isn't that big of a deal in real life. But so long as the environment around you is louder, you can't be heard, which feels a bit unrealistic as well. There is also a voice cast of many people, and the dialogue isn't too bad, except for some lines, with Sam Fisher's sense of humour.
The value can kill should the campaign if the campaign is completed in a breeze. After that, unless you can play online, or don't get bored of the same things over and over easily, there really isn't much to do with it, and it may become another forgotten game.
Overall, Splinter Cell: Chaos Theory is a great game, with stealth, hi-tech items, as well as other things make it worth playing. But if you have to choose between versions, take the XBOX or PC version over the PS2 version, as they are better with visuals alone. But overall, you should buy this game.