Just a note about the 7D sensor.
When the 7D was first announced in 2009, its main competition was the D300. If we compare the sensors in both cameras, the 7D simply blew the D300 away. DPReview described the sensor as 'class leading' and this is supported by DXOMark test results (ignore their silly overall scores).
Fast-forward to 2012: we now have the 5D3 vs D800 sensors. I expected 5D3 to make huge strides in terms of low ISO dynamic range, but Canon made no improvement whatsoever. I don't think many people are too bothered by its lower pixel count vs D800, but the lack of progress in the dynamic range department is rather disappointing, to say the least. Now, if the DPReview early preview test shots for Olympus E-M5 are any indication, it looks like Olympus has achieved the kind of progress one expects from modern sensors these days. I guess this is why many people feel let down by current Canon sensors.
Having said all that, when I needed a FF camera recently, I looked for a few things: optical viewfinder quality, excellent high ISO performance, reliable AF in low light. So, in my book, the 5D3 delivered.
Just some evidence of Canon's successful sales and marketing departments in China, the world's largest market for high-end cameras. From http://news.xinhuanet.com/english/china/2012-04/22/c_131543148.htm
"Although professional cameras are more expensive in China than in other countries, China has a faster growth rate compared with developed economies such as the United States and Japan.
China has already become the largest market for selling our latest high-end camera 5D Mark III, which started to sell last month and has almost sold out now...
High-end digital single lens reflex cameras account for about 50 percent of the total sales of all Canon cameras in China, which is much bigger than other countries..."
Canon clearly knows what they're doing.