Wasn't 500 , it was around 200.
Just letting you know.
I think (not positive) he was referring to the actual nuclear fallout, thus mentioning iwo jima. However, in the Fallout universe, the global nuclear war created enough radiation in the atmosphere that it's still either coming down, or has saturated the earth so much that it's a constant and will be for a good 300 years (at least thats what the vault PA system says).
500 years is a stretch.
Anyway, thats a topic for another thread.
Back on topic, I didn't like the DC ruins (hate is a bit too strong of word). I really hated the metro tunnels after my first or second time having to go through them. I am really hoping we will never HAVE to go underground in New Vegas. What I expect from FO:NV is a lot of desert wasteland, but also a good amount of settlements (possibly even more than in FO3) scattered around, ranging from settlements the size of the republic of dave/arefu, to ones the size of Paradise falls/megaton/rivet city. I'm sure there will be old ruins to explore, but honestly, I don't think we'll be seeing anything like the ruins north, northwest of DC, where the bethesda buildings are, or the corvega factory, etc.
I want an entirely open wasteland, with a good number of settlements, and the giant jewel of the desert in the distance, New Vegas. I am really excited to play this game!