If it is a particularly good (or bad) photo,
I will examine the EXIF information that is embedded in all digital camera photo files.
That gives all the exposure data (shutter speed, etc) and it will let you know if it has been Photoshopped.
Not all photos you find posted on the internet will have EXIF information. Some editing programs will remove EXIF data.
I have seen numerous instances where people mention viewing sample shots as one criteria for determining whether cameras are any good. Now I can see where head to head comparisons can be informative....macro shots, barrel distortion.
However a one off senic shot (no comparisons)????
You have no idea how the photo was taken (what ISO, a particular best shot mode, photoshopped, image size/quality, etc).
I just do get it....maybe it's part of a feel good moment that helps you feel better about a particular camera (as if it's not possible to take a shot)?