It depends what you need. The 5DII was a great sensor encased in a POS body. The 5DIII is a great sensor encased in a great body. Sure it lags behind the D800 in DR, but it's still a very capable piece of hardware.
If Canon put a high DR sensor packaged with a POS AF system, lethargic burst rate, and poor weather sealing in the 5DIII, I'd be shooting Nikon right now. It just so happens that Canon created an extremely well balanced machine in the 5DIII, so I cancelled my D800 order.
For those who value DR above all else, Nikon offers some great options. Everyone's busy humping the D800's 14.4 stops of DR, but the D7000 gets you 13.9 stops for $1,200, and the D5100 gets you 13.6 stops for $700. It seems there are some affordable ways to get all that delicious Nikon DR, so I don't see why the DR lovers are so upset? As a Canon shooter, if DR was the most important element of performance for my shooting needs, I'd be thrilled that Nikon had such affordable options, and pick up some Nikon gear. That's the beauty of competition.
For the millions of landscape photographers that have come out of nowhere lately, you can pick up a D5100 and a 14-24 for less than the price of a D800, and have almost as much DR. That seems like a much more practical way to get your DR fix than complaining about how much Canon sensors suck.