Chancellor Kremlin said:A much better idea would be to have Fallout 0, set at grond zero (ironically). Imagine, being able to play right when the war started and surviving, and having to scavenge a miserable living before any of those small towns and all that developed.
Well I think that would be a good idea. Maybe not while the war is starting though as I prefer to have the 'War' as a kind of mystical cataclysm that no-one really knows how it came about or what happened and they create their myths from this.
Fallout was 80 odd years after the war, FO2 160 years. By the time of Fallout 2 civilization had really started to take hold again, and so it was more of an aftermath of the aftermath. With Fallout 3 being set 200 years after the war and seemingly even more primitive than Fallout 2 it became ridiculous.
Look at how the world has progressed in 200 years. How the US grew. Now even after a nuclear war if there were survivors and a lot of technology survived as well, well it wouldn't be that long to rebuild society back to 'normal'.
What really may have changed is the relations between people, different ideologies and ways of operating for the various city states that would show up. This is interesting as a game concept, like in Fallout 2, but whereas in Fallout 2 the world was still at the tail end of the apocalypse, another Fallout set even after 3 wouldn't really be Fallout anymore.
The early years would be the most interesting in terms of conveying a true wasteland, the later years better for simulating emerging power structures.