In my view, it's always sensible to choose a camera system by looking first at the quality and type of available lenses that are likely to suit your purposes. There are, of course, other considerations, but I would put the quality of available lenses at the top of the list.
When I switched from Minolta to Canon several years ago, before Canon produced its first DSLR, it was the Canon lenses that were the attraction.
There was a bit of indecision between Nikon and Canon because, at that time, Nikon had already produced their first DSLR, the 3mp D1. There were just rumours that Canon were developing a DSLR, so I wasn't 100% certain that Canon was the right choice in the long term.
However, the fact that Canon already had a few good lenses with image stabilisation (the main attraction for me), and 3 tilt & shift lenses as opposed to Nikon's one shift lens with no tilt, was sufficient reason for me to choose Canon in preference to Nikon.
As I recall, Nikon had not introduced their VR system at that time (or maybe they were just beginning to).
For some photographers, and I'm one of them, image stabilisation is a great boon. Most of my photography is done outside of studio conditions and without a tripod. Getting a sufficiently fast shutter speed for the conditions is often a major difficulty. No matter how sharp a lens may be, if the shutter speed is too slow to freeze camera shake, then what's the point?
I have a D700 and 14-24 Nikkor lens. I bought the camera for the lens, not the lens for the camera. I'd like to buy another Nikkor lens to make the D700 a more flexible tool, but I can't see anything in their range that interests me, that is better than the Canon glass I already own. The next lens I buy will probably be the Canon 70-200/F4 IS. Both quality and weight are considerations for me.
The Nikkor 24-70/2.8 would be useful for me, but not as useful as the Canon 24-105 IS on the 5D. Whilst it's probably true that the Nikkor is a slightly sharper lens than the Canon 24-105, it's not necessarily sharper at 70mm and 1/50th sec, hand-held.