Only one that comes to mind is After the Storm (I don’t think it’s similar to Fallout tho? Idk haven’t played Fallout 
). I really liked it! I for one would be interested in seeing more stuff in the vein of apocalypse scenarios.
And well, no idea’s ever really original anymore. I say don’t worry too much about that and embrace the two cakes principle!
I think you should go for it! You’re better off writing something you’re passionate about rather than something you’re not as into but you think would be popular 
Writing a COG story is a huge undertaking from what I’ve seen! Write for yourself first