You have observed the effects of scale.
Digital cameras have shorter focal lengths, and smaller actual apertures. This means that the diameter of the aperture for f8 is much smaller on the small lens of the digital than on the large lens of the SLR. The f-stop relation to depth of field doesn't scale down exactly. Below about 1/64th" aperture, f-stop actually doesn't mean much: you effectively have a pinhole lens. (Cheap point-n-shoot "fixed focus" film cameras take advantage of this, too.)
NB that the actual sharpness of the image is a function of the grain in the image sensor, whether that is a film or a CCD. CCDs have larger grain than film. Detail smaller than the grain will be not be recorded, no matter how finely the lens resolves the image. The effect of this is that fuzziness at a smaller scale than the grain is not recorded, so that the image appears sharper, hence has greater apparent depth of field. IOW, sharpness, and hence apparent depth of field, is as much an effect of how we see an image as of the image itself.
It may be of interest that the best SLR lenses have greater resolving power than most films, and much greater than current CCDs.
BTW, this effect of grain size can fool you when you check the image on the LCD screen. Fuzzy images will seem much sharper on it than when viewed on the computer monitor. Make sure your camera has a play-back zoom function, so that you can check the focus of different areas of the image.
HTH