According to Raptr Guild Wars 2 is my 4th most played game (since I started tracking around a year and a half to two years ago). I love the game and I can't put it down (in fact I only took a break just to make this post XD). I'm a level 80 Ele (Elementalist) and to me it's a really fun class. There are so many weapon setups you can have, plus each one has 4 different element types (I really only use 3).
What I love about the game is the exploring, it's really open and a really big world. Other MMOs I played I liked to wait until others got on and we'd play together. But this one I just like to walk around and explore (not to say I don't like groups).
If you like open world games then I'd give it a shot.