Peter van den Hamer, a Dutch physicist, has written a very interesting four-section (see the navigation buttons at the top) article looking at DxOMark’s sensor tests. This independent analysis indicates that the DxO guys are doing a pretty good job. My big Canon system, sadly, ends up in the “losers” category along with medium-format sensors. Nikon, Sony, and other users of the Sony sensors are crushing everyone else. van den Hamer notes that Olympus is beginning to close the gap. What he didn’t say is that they did this by buying sensors from… Sony (source).
[Separately, DxOMark has tested a new Nikon D5200 APS-C (smallish) sensor camera and the result was a 14 f-stop dynamic range (Canon SLRs manage between 11 and 12). What's unusual about this test is that the sensor is made by Toshiba. So now there are at least two sensor manufacturers that can easily outperform anything that Canon makes in-house. As DxO says in their conclusion: "The new sensors comfortably out-perform the current Canon offerings in practically every metric."]