I've been playing quite a bit of World of Warcraft over the last few weeks. Not a huge amount, mind you, but enough to progress from "total clueless newbie" to just "somewhat green".
I've tried a few MMORPGs in the past. I tried Ultima Online soon after it was released and gave up after a few days. I came back a year or two later and played it on and off with an online friend who had vanished completely into the game, but it just didn't stick.
Everquest, if memory serves me correctly, had me playing for all of three hours before I decided it wasn't for me. The Sims Online was a really neat chat-room hobbled by a painfully bad in-game economy, and insufficient mass-appeal.
World of Warcraft, on the other hand, sucked me in quite effectively. I think what really did it was the well-designed quest system. From the moment you appear in the world of Azeroth, you're not just plonked down in a free-form world and left to your own devices, you're given things to do. The game is balanced so that you can do most of these things alone if you want, but sometimes you might form an ad-hoc group with other people at the same level of questing to finish off a particular foe.
This is neat, because it's like being back in one of the old Ultima games, before they started sucking. The world is full of people with problems, big or small, and your job as the hero is to go around solving them. But instead of the world being populated with filler characters who can only say "I'm too busy to talk right now", it's full of other real people, who can only say "STFU n00b".
I like the questing, because the social aspects of the game are really only a cool background thing. It's nice to occasionally grab other people to help with quests, but given I'm only a casual player, logging in at random times when I'm not busy with something else, the chance of even meeting the same person more than once is slim.
The ultimate problem, as I've started to discover, is that thanks to the necessary mechanics of an MMORPG servicing hundreds of thousands of users, questing is a frustrating thing. In the Ultima games, after you'd cleansed some town of the evil that had been afflicting it, the evil would be gone, and the town would be full of villagers who would thank you profusely before saying "I'm too busy to talk right now". In an MMORPG, once you've cleansed the town of evil, it hangs in limbo for five minutes... and then resets itself for the next guy.
This behaviour is absolutely necessary for the game to work, but at the same time you're left feeling powerless. I mean what's the point of doing the quests in the first place, if you're not really ridding the world of that ancient darkness, and the big evil red crystal will be there for hundreds of thousands of other people to destroy every day for the lifetime of the game?
It's no wonder that games like this quickly end up revolving around leveling and getting more powerful items - you can't change the world around you one iota, so the only thing you have the power to do is change yourself.