World of Warcrack
World of Warcraft is the popular MMO from Blizzard Entertainment, but I'm Sure you already know this. The game centers around the world of Azeroth, and in the expansion Burning Crusade; Outland. You can create several characters. They can be on either side of the war, Horde or alliance. You also have several choices in classes (mage, warlock, warrior, paladin, etc.) which allow you to level your character through questing and completing dungeons all the way to level 70.
The game does this very well, it allows you to emerse yourself in the world, and have alot of fun while doing so. Theres something for everyone in this game. You can play PVE, PvP, you could Roleplay, play the economy, and theres several other choices. Obviously, with so many choices in gameplay, and so much depth, the game can become extremely addictive. Whether thats a good thing, or a bad thing, you decide.
There is a monthly fee of $15.00 a month for the game. Although, it makes sense for Blizzard to do this, to pay for maintence, servers, and gain some profit along the way, at times, it doesn't seem worth it to shell out that much cash to play a game.
If you're a bit uneasy about trying the game out, try the 10 day free trial available on the world of warcraft website. On the whole however, World of Warcraft is a great game with alot of depth that should keep most players addicted for a long, long time.