It's true that radiation will never actually create nor sustain life. It can only destroy (or, for sticklers, render unusable) information stored in DNA helices by slamming into them like a hail of bullets. There is one known, practical usage of radiation-as-DNA-slicer, and that is in genetic horticulture: By shotgunning legions of plant cell cultures with radiation and sorting through the remnants (or "inducing mutagenesis" as they call it), genetic horticulturalists (or would that be horticultural geneticists?) can find useful mutations. This is a bit like blasting numerous racks hung with sheets of paper with shotgun shells over and over again, then sorting through them later to find a few punched out in the pattern of a smiley face.
So yes, radiation-empowered creatures of any kind (especially those who were irradiated in any post-zygotic life stage) are sheer fiction, pure science fantasy.
Ghosts, on the other hand, are not science fantasy, but rather mythological/folkloric fantasy. Therefore, by adding ghosts to a franchise like Fallout, you're mixing metaphors in the context of the suspension of disbelief; or, put another way, here's what you're saying: "People who enjoy appropriate fictional material in their fictional games have no grounds to dislike incongruous fictional elements also being added to those games."
To sum up, your argument has been thoroughly torpedoed. It's plain and simply true that F2 has too many pop-culture references and other such incongruous rubbish, although I personally enjoyed them at the time, having been conditioned to them by various point-and-click adventure games of the 1990s (notably Space Quest, Quest for Glory, and King's Quest).
