They're not even comparable. One makes millions and millions of dollars more than the other, one is marketed more, one has more fans & paying customers.
I don't understand why you even ask.
But, exactly as FlyingToast said
There's a really large thread over this in the MMO section of the forums.
One could make the argument clicking repeatedly on a tree all day long is boring as well.
I've only played WOW a little bit, but I did think it was fun. It's just a different game, both RS and WOW appeal to different types of players. I don't think one game is necessarily better than the other.