Personally, ditch anything resembling FC's and characters from already published media.
I don't want to see someone else's vision of SuperMan, I want to see an original creation out of their imagination that sure, might be based on Big Blue but isn't going to murder anyone else's idea of SuperMan.
You run into it a lot on FC games where someone will change a characters sexuality, or just interpret it other than what is stated in the comics.
For one example: The original Ice Man (Bobby Drake) wasn't Homosexual, he was always dating women, he wasn't good at it, but there was no sign that he was playing for the other team (This was before the students brought forwards story arc where /that/ original Bobby is homosexual) but on some games that featured FC's there was tons of demand for someone to make Bobby gay just because they thought he should be. I personally never saw him as gay, even though I am not exactly straight myself, so those demands came off as unwanted and weird to me.
TL;DR nobody's idea of a FC is going to fit everyone else's idea for an FC. So just don't.
There's also /plenty/ of games that people can play FC's, you want new blood, try something new.
As for system, yeah M&M has a couple games but the system has some serious issues (You have to buy a bulletproof power for 5 points to be immune to bullets, but you can't be immune to knives, just bullets. Go figure, for example.) along with some really easy ways to break the PL system through Feats/Advantages.
There's one Aberrant game I know of, it's really small last I checked but Aberrant has the issue of low starting points by the book, it's hard to be really /good/ unless you're hyper focused.
Savage Worlds has some fan base, as does a few others. I think there's a couple FS3 super hero games as well. I know there is still at least one Champions game but that is way to crunchy for most casual or newbies to the system.
Personally, I still want to see an old FASERIP game updated for use with a mush, with random rolled creation and everything 