In several fora, it has been noted that those are traced pictures.
Many artists frown when they hear the word talent, when it is a case of patience, and technical knowledge.
There is only one that I'd put apart in the group pictured there, and it would be Bert Monroy, first, because he does not trace on top of the image, then use the gradient mesh function, but he creates each element, using and developping his own techniques, second because he is adding insane levels of details that might not even be visible in the final piece (I remember that once, he created the vue of a virtual future city, and one one window, there was a desk, on this desk were some CD's... he had in fact created the text on the CD's in Illustrator, even if the Cd was a few pixels wide on the final image.
Personnaly, I find that those are nice renderings, but I'd really like to see personnal pieces that come from the imagination of those illustrators...