Consider these following examples if you will. in FO2 there's a ghost which you must retrieve a locket for. Honestly which is more likely, a supernatural spirit or two well defended factions pushing east over the course of many years? Also in FO2, there's an awesome Monty Python reference of the bridge keeper. I was very surprised when I saw this. but not the angry surprised, like how so many reacted when they found Harold or the infamous alien.
In short, what I'm hoping to demonstrate is that Fallout was never really known for it's realism, and it truly is unfair to hold Fallout 3 to a higher standard. I'll leave you with this: Can you imagine if Black Isles never implemented the *SPOILER, I assume* talking Death Claws into Fallout 2, and instead Beth. introduced them into FO3? I betcha it would be vehemently regarded as total b.s.!
-Ant