it's debatable for some, I think it is. I've spent somewhere around $250 on WoW in my time playing and I've gotten at least 30+ days of played time. Look at it from the perspective of if you bought modern warefare for $60, how many hours did you get out of it before you spend another $60 on another game and put modern warefare away.
The amount of enjoyment and played time that I've gotten out of WoW totally justifies the amount of money that I spent on it. All though I'd say if you're just starting it then it's a pretty expensive game to get into because you've gotta buy the game, and then 3 expansions, so it's at least $100 to start, but they offer a lot of free trials so you can really test it out and see if you want to get into it.
overall though the end game caters to all kinds of players, anyone from casual to hardcore, you can find enjoyment and there's always something you can do to get better. And I don't think the community is rivaled by any game.
I can't say anything about Rift as I haven't played it, but graphics wise it stomps WoW but so does just about every game out there, but part of wow's draw if for people who are running older systems and who don't have the money to upgrade or don't care that they get under 30fps.