I think it has a lot of key elements that more MMORPG games should have....
I'm not much for PvP, but that's another great aspect of this game, it's not all about the PvP like World of Warcraft and Lineage II, there is a real story to it. World of Warcraft, Lineage II, Eve Online, Silkroad, all of these games have strong stories behind them, but there is no story in them.
A major misunderstanding with this game is the level 20 cap they have on the characters. The point of the game is not to level up and become the god of all other players, it's to play through the storyline and get insane gear. There are bigger goals than leveling, like I said there is armor, ranks, exploration points, mini quests, mini missions, rare and collectible items, and stuff like that.
Guild Wars is in my opinion the best RPG out there right now. Its team-based gameplay is extremely well done, and the graphics are a nice touch as well. I would definitely recommend this game to anyone who likes team-based games with a lot of thinking involved.