A word of warning, don't get engrossed or addicted to them. It can suck your time away. I used to play Runescape years ago and I would say that I spent far too much time on that game. Wouldn't recommend playing Runescape now though, some of the changes
Jagex made are really lame, but I did enjoy it back when I used to play it.
World of Warcraft is probably the biggest MMORPG. Guild War 2 is fairly new and popular and received good reception.
I may as well mention that Star War: The Old Republic is a recent MMORPG. Bioware added a free-to-play option to it, however I've read that the free-to-play option is quite restrictive. Might be worth trying though to see if it's worth paying for the full
Hey mate. I used to play World of Warcraft for years (far too much!!). I absolutely love that game (especially Vanilla and Burning Crusade), I still miss it from time to time, but my circumstances have changed since I used to play, and I don't have the
time to dedicate to it any more.
I'd certainly recommend it if you have plenty of spare time.
I wonder if the next gen xbox's will have a decent, popular MMORPG?