I don't know quite how to describe the difference and I don't have any of my buddy's photos to put up as a comparison. I believe the right way to put it is that compact digital cameras have lower dynamic range sensitivity which makes background appear to be more flat or muddled because the color differences are less. I do believe lenses play a significant role in this.
When you look at background (that part of the picture behind the field of focus) larger/faster/more sensitive lenses reveal more detail of what is there. This is especially important in underwater digital photography using water or sky as backgrounds. With a digital compact the non-focused part of your background can fade into a color field stripe of blue or green that can be 5-10% of the vertical space of your photo. (you can see this when you adjust contrast or if you do color replacement.) With a better lens and sensor that stripe will be much smaller and you will have more similar colors next to each other rather than a single field. This is not purely an artifact of the JPEG compression (though JPEG compression makes it worse by trying to link similar colors into color fields).
Hope you can get something out of that! There still is information in the non-focused parts of the image and it less with the digital compact camera. Foreground tends to suffer from this less because there is more light and stronger contrast because of common subjects that people takes photos of
