A unique experience
The story is made from loose lines slowly entwining as the game processes. In prophecies the main "bad guys" are The Charr ( Furry Cat/human creatures) and the Stone Summit ( Tiny armor-clad dwarfs) which will do everything in their power to stop you. The game is instance based which means it's built up with areas connected through portals instead of one massive world. Inside the towns and outposts you can chat and trade with other players but outside you can only play with a party of players that you set up in the outpost before leaving.
There are six professions in Guild Wars prophecies (which you can attend as primary or secondary). Ranger, monk, warrior, mesmer, elementalist and necromancer, each one of them having their own set of skills. Skills play the biggest role in defeating enemies and surviving. There are lots of skills that turns the tide of battle, in GW you depend more on your skills than your weapon and armor (those are more like bonuses). The AI is good and the enemies are very challenging. Sometimes they even put up a huge struggle leaving you with 60 Death Penalty and great anger.
Strategy, skill and experience is the key in this game not levels and armor. If you want a good customizable mmo experience that doesn't require you to play all day long to keep up with your friends and that doesn't rely on monthly fees, give Guild Wars a try.
Guild Wars is the best choice when you're going to take the first step into MMO-Land and it has enough content to make you stay.
Just remember that MMO's can be very addicting, play moderately!