there's a lot of factors to "graphics" you have lighting, shading, textures, colour pallet, as well as mip maping , bump maping, polygons then AA quality or which it uses and all that other stuff..
you could have the exact same everything but change any one of those and people would debate whether graphics were good. just using colours that some deem too vibrant would cause a debate.
And people can use the same engine with the same tech doing the same amount of work but that does not mean that it will look the same.
So im not quite sure which part of graphics you are saying is not subjective.
Some parts are measurable no doubt, but the overall out come will never be the same even if the measurable parts are equal "resolution, polygons, aa, etc"; the outcome will be subjective, and the outcome is "graphics"
now if we compare this:
to this:
and we debate which looks better it will end up being a subjective debate.. one uses some blurring smudging the textures up a bit and adds some fogging effect. but for the most part uses a better pallet.
the other one has a much more crisp look not blurring things, but also suffers a bit because of that. and color vibrancy is a bit high. the fogging effect is more uniformed and so obscures less of the area, and atleast from a distance trees seem to look better. (or do they?)
the games aren't any where near the same age at all.. but people can and will pick and chose parts that are more palatable.
they can also for the most part describe what part of each is displeasing. But what is not pleasing to me may be pleasing to you..
and that is without entering in to the art style debate where you have games like borderlands.
Im not saying fallout looks as good as it could. im not saying it looks as good as some other games that probably spent the same money. All im saying is the games that look better for the same money are lacking in other departments, its a balance all game devs have to address. and in the case of fallout. im sorry but they are right to prioritize graphics lower than core game features, and i think others should do the same.