Phantasy Star Universe is a good game, brought down by many flaws.
The single player mode is split into 12 chapters much like a TV series, with opening and ending theme songs for each chapter as well as a sneak preview of the next chapter. Though in total it takes about 25 - 30 hours to finish.
The main character for this saga is the 17 year old Ethan Waber, a young orphen brimming with hatred for the local law enfocement known as the Guardians. While meeting his sister at the Guardians colony, they are attacked by strange monsters known as the Seed. During this attack Ethan acknowledges he isn't strong enough to protect those he loves, and decides to join the much hated Guardians.
The story is cliched and cheesy at best, it has the love interest, the spikey haired teenager with an unknown past saving the world, And much to my dismay, the dialogue and voice acting make the story even worse to follow then it needed to be. Some of it was beyond the pain barrier.
As for the way the game plays? at the start of each chapter you have a cutscene telling you a tid bit of the story, meet up with some AI characters who, and lets face it, are as useless as a chocolate tea pot. You then travel to another planet, hack your way through a very repetitive dungeun, fighting mindless enemies, beat a boss. Rinse and repeat.
The online mode plays out in a very similar manner, only it's alot more fun fighting huge bosses with other people who do more then just die like their AI counterparts. In creating an online character there are quite a few options, picking from race, class, and appearence. The first two have a great result on your stats and skills, while your appearence does nothing but satisfy your vanity. During questing you can have up to six party members as you travel through various missions. The missions themselves are split up so that you can create one, or join one already in progress. Though they have different tiers of difficulty restricted by the player level. So that people don't bite off more then they can chew. In the dungeuns there are many items to be found, either inside barrels, hatstaks, or occasionally dropped by enemies. These items can be used to create weapons, armour, and other useful equipment from your user room pet robot (in which you can even name and upgrade). If you wish you can even have your own user store to sell the items you have found or created, this is actually a necessity if you ever hope to get enough money to get the higher class weapons.
Graphically PSU is a disaster, it is obviously a PS2 port and therefor looks terrible on the 360. There are alot of jaggies and low res textures. However the art style and vibrant colours help to make up for it's lack of polish.
Phantasy Star Universe is a game you either love or hate. The graphics aren't next gen, the voice acting and story are rather skittish, the AI is terrible, and the game play is monotoous. Yet, despite all that it can still be very addictive and quite fun. especially online. But if you are thinking about getting it for the single player alone i would avoid it.