I've played a lot of MMOs, but though I enjoyed things like Lord of the Rings Online, and World of Warcraft, there's only 3 games I ever felt like playing for a very long time.
All three shut down.
Of them, I can only re-enter City of Heroes. I've heard nothing of a rejuvenation of either of the two others, and they were both incomplete in some way, more or less sabotaged by parts of their development teams, leading to their demise. (Tabula Rasa & Firefall)
Though I wish for the best versions of the others to return, CoH is the one I thought about consistently when it wasn't available. Besides, CoH has the nicest community of any MMO I've played in the past 15 years. That's worth the price of admission. Well, when there was a price.