Diablo II:Lord of Destruction is a third person rpg where the player take the role of a hero which has to save the world. I like these games with some rpg depth (or much) . The multiplayer part of the game is where the real fun begins.

The singleplayer part could be used as training for the multiplayer part. The game uses a online function called battle.

net
You create your role-play person and then set out on adventures. There is several classes to choose between so you will certainly find a class which suits you gameplay.

You then can create your own game on which other players can join your quest to destroy demons. I think this is a good way to set the whole thing up.

Of course you can join other games created by fellow player. A excellent game which will take a while to die out.