I think that CoH has very devoted fans...
If you were to be able to get a hold of the numbers for how many people come back to CoH after leaving, I think you'll find that the number is far higher for CoX than for most other MMOs...course, I could be wrong...it's happened before... 
If the other threads about MMOs on that forum are any indication, this is true. None of them have grown to be more than a quarter the size of the COX thread, and that's being extremely generous.
Wow! City of Heroes even beat out the Panty Explosion thread! 
I just figured I should share this picture- but first it needs some explanation.
This is a cropped screenshot from a forum for another game- a tabletop miniatures game. It's taken from the Off-Topic forum, which is not visible to people who aren't members. And there's one topic in that forum that has grown to legendary status, simply for its size and tenacity.
So what is this one topic that has people talking about it?
I'll give you three guesses, first two don't count.
Ninth one from the bottom, or 10th from the top. Your choice.
Worth noting also that 1) It's not the first thread on the subject, and 2) The thread was started on August 14th, 2004. The screenshot was taken earlier today.