The sharpness setting of zero appears to mean 'apply no sharpening at all', hence the image that is captured is soft due to the anti aliasing filter. The default setting for Standard Picture Style is 3, and for Landscape, 4. These two settings are a good middle ground between too soft and sharpening halos, which are highly visible at the highest setting of 7, and in general one of these middle settings (3, 4, or 5) will give the best-balanced results for most purposes. You also have to remember that these are 100% crops viewed on screen, and considering the high resolution of the 5D Mark II, even moderate sharpening levels can produce sharp prints up to moderate sizes, or for viewing on screen.
Sharpness: 0 (Default for Neutral and Faithful Picture Styles)