I'd like to say that I'm still here, but I've got to admit, the Flash as I had him written's lost his allure. I can't see a way to move forward with him, and while I do have a few backup options, it all depends on GM/Co-GM approval. 

I'd start with pitching Sonic, what with having a CS primed and ready, but having heard [@Gowi]'s opinion, which I completely understand, I don't think he's a viable option. 

My second option would be something I'd been discussing with Wraith prior to the game's decline, that being me taking over Spider-Man duty, playing both an established Peter (which would require either a time skip or a reboot) and a newbie Miles. So, playing the "Spider-Men", in a sort-of not really teacher-student relationship. I have a CS that'll be ready with a few tweaks here and there, but again, it's all up to GM approval (and a time skip in-game). 
[sub]Although now that I think about it, a retcon could work, if that's an option at all...[/sub]

In regards to feedback/criticism, all I can say is that after participating in three games of this style, one of them being my own, I think the primary reason for loss of interest is the lack of engagement. By that, I mean that players are given so much freedom, and the overarching plot is pushed so far to the background, that eventually everyone's left thinking, "Now what?" So, long story short, I think a way to guarantee the game lasting longer is to put more emphasis on the main plot. Retain the sandbox element, but with a larger focus on the bigger scope of things. I hope that made sense.

And with that,
/endramble