Think about it; if Fallout 2 was made, exactly the same way it is now, today, do you believe that it would get passed the rating board with only an M rating? Personally, I doubt it. Much of what made that game awesome was how "real" and dark it was. Real in that it didn't have any Deus Ex Machina explaining away all the IRL horror that the game shows and dark in that many of these horrors are joked about. Things like [censored], child molestation, six, drug use, alcoholism, murder, gruesome violence and even bestiality. Even with the same graphics the original games have, I really don't think if they went through the rating board, they would get anything lower than an advlts Only (AO) rating; which means that, at least in the United States, no retail outlet would carry it.
Now try to imagine all that same imagery from FO1 and FO2 that was mostly described through TEXT, now shown in all it's modern day high definition 3D glory. Not even gonna fly. The violence will stay, but in order to keep the rating down where it needs to be, other things must be compromised. We have already seen, in Fallout 3, the rating board demolish kill-able children. There is, as far as I can remember anyway, no mention of [censored] at all in Fallout 3. There's just violence and some sporadic use of coarse language. You can't even get laid, even though there is at least one [censored] in the game (maybe you can screw her, but she never wanted me even if I paid). They sure as hell don't have any shady porm studios where you can get poisoned after going in the back and waxing some shafts for 5 caps.