I got into the game soon after launch. I think it was perhaps a month old. Prior to that, I hadn't heard of it at all but had heard of the MMO concept since hearing about WoW was practically unavoidable at the time. I was a hard NO on the concept as the idea of paying full price for a game and then having to shell out a sub to keep playing sounded downright diabolical. But a good friend of mine got to playing CoH early on and talking it up and I was like, fine, show me. So he did. And that was when a big fishhook spooled out of the internet, hooked me by the wallet, and reeled me in. I ended up having a continuous sub from then till they shut down. I was there when the servers went dark, torch held high in AP.
From there, I recall the various rumors and questions of whether someone might buy the game and revive it, whether enough pestering of NC might get them to change their mind and revive it, and all the whispers of there being a private server somewhere out there. There were of course plenty of discussions of fan groups trying to start up their own successor project too. I even backed CoT and still hold the hope they will eventually launch with something great. Time will tell.
Eventually of course, those rumors of a rogue server proved true and then spawned the varied private servers we have now. I got on HC early on, played for a bit, and then dropped out as other things took priority. And then a bit ago, some friends I used to play with told me they were back and so, I am too.
I think the key selling point for me was the customization. I could play my own hero, or later, villain, and I was the center of my own story. The game had big central heroes and villains, but they were more flavor than substance to me. I was the central character of the game, (everyone was), and I didn't feel like I was standing in Statesman's shadow. That was an important part of the game to me and something I didn't consider possible in a Marvel or DC MMO, should one ever come out. Everyone knows who the big dogs of those universes are and not having them front and center in a game based in their universe is just impossible. I didn't want to just play as one of their heroes, and I knew if they allowed me to make my own, I would be relegated to being in the big dogs' shadows. (And that's basically what happened so far as I know.) Champions sounded a bit interesting as a pseudo clone of CoH, but CoH already scratched that itch and I didn't really care for the art style. So CoH stayed my home until it couldn't be any more.