Possibly the best no monthly fee MMO there is.
Guild Wars 2 is on its way, so this game will be pretty dead soon.
The game costs a single fee, but there are no reoccurring monthly fees, so you won't feel like you've wasted a lot of money if you decide you don't like it.
If you are going to get this game, I would suggest also getting an expansion, like Factions or Nightfall (Eye of the North is different), because hardly anybody plays the original anymore. It will be hard to find players to do missions with and you will end up playing by yourself, using the provided computer henchmen.
These henchmen are actually a good feature, you can use them at any time, say if you don't want to play with other players at the moment, but want to finish a quest, or maybe even farm gold.
The game is unlike WoW in that you do not roam the free world. The towns each have their own instance mission which you have to complete to get to the next town. That instance is the area on the map that you travel. Everyone meets up in these towns and make groups, so it's not that hard to find people to play with. You can basically teleport from town to town once you have already reached them, there is no travel system.
The only problem is that with so many expansions it has stretched out the population over the areas, so there are less people to play with.
The game system can seem a little complicated for a new player, about the same as WoW. I will explain the basics -
You make a character, choose your main class, Warrior, Monk, Elementalist, etc. Later you will get to choose your secondary class and will be able to use some of it's skills. You can combined any two classes, there are no limitations.
The level cap is at 20, but enemies can range far beyond that, so it takes group effort and cooperation to complete a mission.
As you level, you gain points which you spend on Attributes. In order to use weapons and shields, you must have the required attribute levels or they won't be affective. These points also increase your skill powers. You can always adjust your points, it does not cost any gold.
You can have a total of 8 skills on your action bar at one time, unlock and use the right skills together and you can creative some devastating effects on your enemies.
Skills use energy (mana) points, which each class has. Some weapons and add-ons increase your energy, some can even take it away in order to gain something else.
The more mobs you kill, the higher your team's stats will rise, but if you die, you will be sent back to the last checkpoint, unless resurrected, and your stats will decrease by a certain % every time, eventually making it so you are not strong enough to continue on the mission.
They are probably the best I've seen for an MMO, besides Age of Conan. They are a little dated by now, but can still stand up to the old WoW, maybe not BC or Lich King.
The world is highly detailed and very big, and that's not even talking about the expansions. Rolling hills, green meadows, snowy mountains, volcanic caverns and more.
I would suggest a graphics card no less than 256mb and 1-2gb ram.
The entire soundtrack was digitally composed by Jeremy Soule. It's has some of the best orchestrated songs I have heard in a game. You probably won't get tired of listening to them any time soon. This soundtrack is a masterpiece of its own.
This game is not as open an free as WoW, but it is not supposed to be. It is its own game with its own playing style, and if you are up for a challenge, play within its boundaries. There are many things to do within this game world, if you are looking for something new, come check out this MMO!