As I try to pull together the gazillion threads of thought in regards to what I want to run next, the second and fairly obvious thing to consider is whether I want to run a superhero RPG again.
There's a lot to things that suggest that a supers RPG would be a good option. It is really, really simple to justify the rotating cast of characters, particularly if you are building the game around a large group of PC heroes who are in a "Justice League Unlimited" kind of situation. As I try to set up a schedule for the other two RPG's my group is doing, I'm acutely aware of how different everyone's schedule is, and the unlikelihood that everyone can make every session.
Perhaps the biggest selling point of the genre is that it is a personal favorite of mine. I'm less likely to burn out I suspect if I am really enjoying the game. This is a double edged sword, however, because I'm what Aaron Allston called a "genre fiend" when it comes to superhero games, which leads me right into the next point...
One of the biggest issues with the superhero RPG option is the problem of tone. Every major literary genre has a wide spectrum of tone. Take fantasy for example. You have the grimdark and very adult fantasy popularized by The Game of Thrones, and you have the lighthearted whimsical fantasy of Willow or The Hobbit. The same is true for science fiction, which spans from the gritty, hard sci-fi to the space operatic. But, and you can argue this point with me if you like, the superhero genre has a massive spectrum in place because the genre can get downright cartoony (literally) to the disturbingly gritty. Furthermore, because I think as a genre comic book superheroes are less well-known than other genres, many players only have a fairly limited sense of what the genre can look like. If all you know are the Superfriends, then you'll go into a superhero RPG thinking Superfriends. Maybe I'm overstating this, but in conversations with other people who have tried to run supers RPG's, I hear about this problem all the time.
Related to this is the issue that as a genre it isn't as popular with some people. I think superheroes have the stigma of being somewhat juvenile, despite the massive popularity of the MCU movies, Arrow, and the Flash. There are players in my own group who will jump on board any fantasy or sci-fi RPG I throw against the wall but give me a turned-up nose regarding superheroes. Maybe it is a sense that the genre is campy, or defies logic, or lends itself to crypto-fascism--I have no idea because I'm on the inside loving the genre.
Thoughts always welcome!