There are obviously differences in the attention that each area has received, and sometimes it's clearly visible that the area has been mapped with tiling textures and then someone moved in with the stamping tool to remove the repetition.
But most places do look more varied, hand crafted, richer, you can really see how nearly every element has been created uniquely. These scenes are truly impossible to match with any other approach, especially because id has managed to hire some of the best artists in the entire industry and they really delivered their best work here, free from most of the usual constraints.
Just to put it in perspective, the amount of texture data used in most of these areas is so big that without virtual texturing, even a single scene would probably be impossible to render on the consoles, or a PC with a 1GB graphics card.