I don't remember specifically how I heard about the game but I ended up joining a super group that had formed even before beta. The City of Heroes website at time was still showing independent power selections, before the power sets and archetypes. So pretty early in the design phase; of course things would change much by the time of launch.
The whole superhero concept and the idea of lots of customization was very appealing. My previous experience with MMOs was EverQuest, Dark Age of Camelot, Asheron's Call, and a few others.
So I started with beta and continued until sunset. I never knew about the secret server, but as soon as I got wind that it was opening up I joined 6 years ago. I don't even remember how I heard about homecoming.
I stay for a couple of reasons, one, the game content itself is very easy to fit a lot of different concepts in: want to play a vampire cyborg? How about a punisher style mercenary? Or a golden age flying superhero? Plus the game lends itself very easily to casual gameplay compared to many other games where grinding and elitism suck the enjoyment. I've done that before no desire to do that again.
The other major reason I stay is because of the community on the forums and live in the game. Even though I PUG 100% of the time and haven't been in an SG since live, it's overall a very welcoming and supportive group of people, with fantastic ideas and great imaginations, ready to lend a hand to others. I played in many many MMO communities, and even after the snap and the relaunch, City of Heroes community still is tops.