Usually, image fidelity, in descending order of quality, is YPbPr, S-video, composite video (NTSC), and RF composite NTSC (coax). It's useful to hook them all up, IMO, since cables are cheap compared to displays. There are numerous posts in the hardware forum and elsewhere on component cables. Don't get the cheapest, and for short/moderate cable runs there's no need for very costly brands. Since program sources vary widely in quality, switching to various inputs may filter out artifacts, although this usually reduces image resolution, too.
Often see complaints about the compression used for both SD and HDTV by DBS services (and cable TV or multicasting OTA stations). The clearer DVD images suggests that could be the fuzziness problem. Also, since you seemed to using RF NTSC (coax) generally, which is the lowest-resolution most heavily filtered signal source, that seems be a source of fuzziness when 'soft' images are greatly enlarged. H/DTV images shouldn't look fuzzy at all, although there's a range of quality between programs and sources. -- John