Not so shocking, actually. The 5D is a pro camera, and you're expected to pull the RAW data into Lightroom and manually tweak and tune the final product. Its output is optimized for this workflow: minimum processing in-camera, maximum options later.
The iPhone's software, on the other hand, is doing some auto-adjustment before the file hits the SD card. It's optimized for a decent photo without any manual steps.
Also, notice the distortion in the iPhone photo: the buildings "lean" towards each other. The Canon 24-70mm f/2.8 is a _nice_ piece of glass, and is worth every penny of its $1500 asking price.
tl;dr: Take the 5D shot (in RAW, hopefully) and let a pro have a shot at it in Lightroom. That's a fair comparison.
The 5DII would have also been more accurately compared with the Canon EF 24mm f/1.4L II lens (according to the Exif data the sample photo was shot at 24mm).
The iPhone 4S's camera is a fixed focal length while the Canon lens they used is a zoom lens. Zoom lenses trade certain attributes for the flexibility of being able to zoom, one of which is corner softness at wide open apertures. The 24-70 is a decent all-around lens, and I have used it extensively, but I have never encountered a zoom lens that reaches the same image quality as a fixed lens for the same focal length.
With those little bitty scaled-down snaps, there ought to be no discernible corner softness with a big 2.8 pro zoom (and IMHO there isn't); we're mostly eyeballing center sharpness, white balance, and range of contrast. Of course there'd be less barrel distortion with a prime... but it doesn't stand out either way with these scenes.
You can see there's a little less blowout on the shiny roof with the 5D, and quite a bit more detail in the shadowed city streets. Certainly a higher color temperature, probably more accurate. But the 4S is quite impressive nevertheless. No apparent vignette issues.
These photos are not useful for assessing high ISO noise/grain...
Or blow up a small area (within the focus plane), and see which is sharper. Or better still, take a photo of a moving target at night.
One advantage of a DSLR is that you can get a sharper photo with less light and a shorter exposure time. On web-sized photo, taken on a sunny day, you just can't see the difference. If you take a photo at night even a complete amateur like me can tell the difference.
A DSLR isn't like a Ferrari, which blows the competition away in favorable conditions. It's like a Four wheel drive that can be used anywhere.
The iPhone's software, on the other hand, is doing some auto-adjustment before the file hits the SD card. It's optimized for a decent photo without any manual steps.
Also, notice the distortion in the iPhone photo: the buildings "lean" towards each other. The Canon 24-70mm f/2.8 is a _nice_ piece of glass, and is worth every penny of its $1500 asking price.
tl;dr: Take the 5D shot (in RAW, hopefully) and let a pro have a shot at it in Lightroom. That's a fair comparison.