Fallout has a lot more elements that the engine has to keep track of as permanent denizens of the world. The game will be packed with a lot more talking, relevant characters, items and physics objects, and all of that takes a toll development wise. Fallout is a much bigger game than most of those others for reasons I don't even feel like I ought to have to explain, I mean, you've played them, right? Fallout is a bit different from something like inFamous or even Witcher 3 where much of the world is static, simple, and doesn't change much based on your actions.
but when you omit context, purposely or otherwise, that means there's little to no value in that comparison.