City of Heroes still has, to my tastes, the best character generation system of any MMO on the market. The number of powerset combinations available to choose from is staggering, and the appearance generation system will let you come up with at least a rough approximation on pretty much any humanoid you can dream up. There are also some really unique archetypes in CoH such as controllers (extremely powerful crowd control specialists) and master minds (pet users that are can summon swarms of pets) that don't really have close analogues in other MMOs. Finally, the game has one of the most robust systems around for letting players create their own content. Some of the best story arcs to be found in CoH are in player crafted missions.
I will admit that City of Heroes is a MMO that I only ever seem to enjoy in one month stints. I think my overall problem is that the pace of advancement seems to slow to a crawl by some time in the mid levels. But those one month stints are always incredibly fun. Dreaming up a crazy new character design and taking it out for a spin is simply more of a blast in CoH than any other MMO I've played.
The sad thing is that I suspect that CoH is actually still at least a bit into the black. I don't see how Paragon could have put out so much content in the last year if it weren't. If CoH was under SOE, Funcom, Turbine, or really just about any MMO company apart from NCsoft I doubt we'd be having this conversation.