Nikkor lenses with a constant aperture have a golden ring next to the front element. As constant aperture is a synonym for high quality, it would seem that that golden ring is reserved for high quality Nikkor lenses.
I would assume the AF-S VR Zoom-Nikkor 70-200mm f/2.8G IF-ED
to be of at least equal quality as the Canon 70-200mm f/4L.
Likewise for the AF-S Zoom-Nikkor 17-35mm f/2.8D IF-ED
in relation to the Canon 17-40 f/4L.
But I'm not sure.
Notice these Nikkor lenses are much faster (f/2.8) than their Canon counterparts you mention.