It would be interesting to see some story of people living on a nuclear sub, which in a sense could run forever, and surviving for decades post-war. Food would be the main problem I guess, but a creative writer could get around that.
The main thing this makes me think of though is islands in the middle of the ocean, of which there are TONS, inhabited and not. It strikes me as very improbable that every single island in pacific and atlantic with people living on them would have been hit by a bomb. Not only that, but a ship or submarine in the pacifc could have gone to one of these islands and the crew could be living a Swiss Family Robinson-eque life there hundreds of years later.
Could make for cool side stories someday... of course, the nature of videogames makes that unlikely.
You dont have to hit every inch of the planet to destroy the world.
The Fallout history even says the surface of the Earth buckled under the strain...whole continents sunk into boiling oceans, and new mountain ranges rose up out of prairies...
And then you have the fallout. What islands didnt dissapear wouldve been coated in inches of burning hot radioactive ash, dooming the creatures on those islands to certain death.