A very fun, social, interactive environment that was fully realized, entertaining, and still remains the best.
This game is everything a MMO should be. Easy to get into, easy to stay into, and aside from some patch issues, is streamlined and remains generally problem free.
I meant what I said about being easy to get into. Alot of people who wouldn't be caught dead playing video games before WoW, spend 8 hours of their day playing this one.
The visual appeal plays into that. It gives a sense of lightheartedness that's easily accessible. Content is another. There's never a shortage of things to do. Very few people have actually done them all. Hell, very few people actually complete all the quests in a single town, much less the entire game. There are dungeons galore, which could range from a PUG nightmare to a very rewarding 2-3 hours spent exercising well conceived teamwork, and making friends while competing for top spot on damage while you play.
Also, the world itself is large, both physically, and metaphorically. There's alot of places to go in WoW, and all of them are rich with lore. This lore, that has existed since it's conception in the original RTS, to now is very fleshed out, and for the most part, exists and covers every inch of the landscape.
And, with over 7 million people playing, it's a great place for alot of people to socialize, which I feel, is the greatest part of the game, and the reason people keep coming back to it. People make friends here, hell, I've even known people who got married because they met through this game.
Blizzard also does a commendable job keeping the content coming, and giving players new stuff to look forward to, and a reason to come back.
If you're looking for a way to spend your free time, WoW is a great social climate for people to spend their time in. If they have alot of time, they can even find it a rewarding one.
I did, and while I don't play anymore, I certainly don't regret the time I spent playing. It was a unique experience, and a highly recommended one at that.