Creating Holiday City
I've always been skeptical of fake settings in a super hero game. For sure, DC has done a good job with its locations (although they've also been somewhat sloppy with them--how far is Gotham from Metropolis?). I can see why you'd want a fake city for a story: you can do what you want with its history and character. The TV show Gotham does a fantastic job of that.
For RPGs, though, I always wondered "why?" If you are doing Super City then why not just use New York--if your city is where "all the big super-stuff happens" why NOT New York--or Chicago--or, hell, LA if you want a really different flavor (or whatever).
Most games, if they include a setting city, make it fairly generic--I didn't see the point in that.
Then came JAGS Supers. Our primary playtest game took place in Holiday City--the name worked really well for us--and the location had, over the course of a few years of play-test, a good deal of character and flavor. It was Midwestern--an oddity for us. It had a specific history and set of landmarks and so on.
When it came time to figure out the Holiday City world book we decided to use the setting--all the major players worked well in the setting in a way they might not in a real city. Certainly the Mayor of New York has a different impact than the mayor of, say, Denver (who you might have to look up) even though Denver is a big important city.
Super-villains could take over a district in Holiday City and people would just, kind of, well . . . life goes on. For now. That couldn't plausibly happen in New York. So it worked for us.
Now we just have to figure out how we're going to present it--both visually (the above artwork is mine--a trial piece) and figuratively.