You must play this game
The graphics are amazing for a 2D fighter. This is the best they could be for the time the game came out, and any new game would have difficulty beating the graphics in GGX2. The game mixes perfectly drawn 2D sprites with great 3D effects in the sky in the stages. The best example is the boss stage, where the whole place is a red 3D portal type place, with great lightning effects in the background. This game has the best sound in a fighter, ever. There is no doubt about this. A great heavy metal soundtrack, with awesome voice acting (even though it's all Japanese, can you actually expect English voices sounding good? nah). All of the attacks sound like they should, and no sounds sound out of place.
You can play many modes in this game. Arcade, VS, VS CP, Medal of Millionaire, Story, Practice, and Mission. Arcade is your typical arcade style of matches. VS is, well, you know what it is. M.O.M. is a mode where you collect medals after attacking your opponent. The more medals you have at the end, the better score you get. Story follows the stories of all the characters, excluding 2 of the unlockables. Each character has multiple endings (except for Justice, she has only one), and changing the story happens how you determine a match. You can win, lose, Instant Kill (on to those later) the opponent, fast time, slow time, plus other things. Those determine what the story unfolds as. Mission mode has some of the toughest missions on the planet. Mission 45 and 50 take the top spots, as they are near impossible. But the modes seem somewhat lacking for some reason, one more mode would've been nice for some more replay value.
The Guilty Gear series is known most for the Instant Kills, which almost every character has. You can instantly kill your opponent, no matter what the lifebars say. People say that it ruins the gameplay, but pulling an IK off on an opponent who is just a good as you or better, is EXTREMELY difficult. You have to change to the IK mode first, which is blatantly obvious, and your life slowly dribbles down when the IK bar runs out. So IK's are fun to watch, but they are rarely used in gameplay, unless it's the only possible way for you to win. Plus, if you fail connecting an IK, your Tension bar is gone for the rest of the round. The Tension bar is your bar that lets you know when you can do an overdrive, and what not.
Guilty Gear X2 is the best fighting game for the PS2, and I highly recommend it for anyone that has a PS2. Happy gaming.