This game should deffinately be in every PS2 owners game library.
The game takes you on a journey through different time periods, as you are trying to save the earth from a group of aliens called "Timesplitters". They possess a type of crystal that allows them to travel through time. In attempt to get the crystals back, you follow them throughout time, armed with weapons of the different eras at your disposal.
The graphics are not necessarily the best part of the game, but it is not the main thing you worry about while playing the game.
The difficulties are well set. The "Easy" mode is in fact easy. The "Normal" is average; and the "Hard" is actually challenging. When you finish the story (Which can take a while to beat all the levels on "Hard") it has a good variety of challenges for you to explore. Depending on your achievements in the games, you can unlock different multiplayer modes, accessories for your characters, and even different characters to play as.
Not only can you set up your own a match to play in offline, but it also provides a rich multiplayer experience. The game also offers the option to make your own multiplayer levels. This feature is definitely a good feature, but if you are like me, you won't find yourself using it much. When making the multiplayer maps, you are only limited to a few weapons, as apposed to all the weapons in the game when you set up your own match.
All in all, it is a great game, and is definitely worth a look.