What I found really awesome about City was that there were *so many* options for what you could do.
Wanna stick to the Holy Trinity? Hey, if that's your thing then go to town. Wanna make a character who really does only use Brawl? There's a guy who actually did that, and you should hear him describe what he could do with that character. Wanna make an attackless Emp? You sure could! They'd heal like a champ. And how about making an Emp who's not just *fun* to solo, but can take on a +5 boss and his gang with just a few insps and win? I know for a fact that was possible, because I did it myself. Petless Masterminds... Humanform Khelds... those maniac blappers... catgirls who never RPed... the city was chock full of incredible things that should never have worked, and in any other game they probably wouldn't have. But in our city, they weren't merely *possible*... with enough effort, they could be stunningly powerful.
One of the many amazing facets of City was that, not only were weird and crazy ideas possible in the first place... not only were they functional against default difficulty settings... but some of them could be turned into utter monsters. Take support ATs for example - your control and buff/debuff types. The original design said they should be some of the squishiest characters around. So what did the players go and do? They figured out a way to make those ATs some of the strongest possible characters in the entire freaking game. ATs with a full arsenal of debuffs and controls were the ones who could do things like solo Giant Monsters, and Archvillains at +4.
THAT'S what made City awesome to me. THAT'S what made me feel like I was superpowered, and that I was surrounded by people who were superpowered too. It wasn't just that you could do whatever activity you liked. It was that you could take practically any character concept you wanted, no matter how bizarre thematically or mechanically, and bring it to life. You could make it look the way you wanted, and while some cases took more effort than others, you could usually make it playable and fun. Yes, there were limits. Of course there were. But compared to other games, those limits were sky-high.