So you're actually looking at a few things here:
At face value, you're looking at a photo that's presumably been downsampled to be able to compare every camera on an equal footing, because each camera has a different shear MP capability. Just pick the photo that has the highest image quality--- clearly the top left 2, and then sgs6. You should be aware that the top left 2 are not smartphone cameras, but professional/semi professional cameras.
The setting all those photos are taken at is ISO 800. Basically it is a forced exposure, and in this case it is used to detail the effects of noise reduction in each software/camera setup.
I couldn't have explained it better!