World of Warcraft is probably the most recognised title when it comes to MMORPGs. Ever since it's release in 2004 the number of paying players just keeps increasing where now there are millions of them.
The only problem is that I just can't see the appeal. Sure the game world is large, lots of places to go and see but not a lot of things to actually do. The main focus of the game is combat which would be fine (Pretty much all games involve some form of combat after all) if the combat was at all engaging. All it requires from you is some mouse clicks and you can then watch your avatar beat the crap out of an enemy. Not only that but there's no variety in what you can use your skills for. Once you've worked your way up the levels you might expect there to be a little more to do but, alas, the game just encourages you to fight yet another set of bizarre creatures.
Other games of this genre have been known to including "games within the game" or "mini games" and this is what, I believe, WoW really lacks. A simple capture the flag game or a team based attack/defend scenario with objectives would be great. Something that requires you to strategise with your team and use your items and abilities in the best way to aid the situation. Sure there are raid dungeons and the such but really all that entails is defeating hordes of enemies and picking up loot until you reach the inevitable "boss fight".
There are non-combat skills that require you to go out and gather some materials and then turn them into something. Usually into weapons or armour to help your ultimate quest of killing stuff.
Basically if you like repetetive combat and not much more then World of Warcraft might just be for you. Otherwise, however, there are plenty more varied, engaging experiences out there so I suggest you scope out some other choices before settling on this.