DVD's, and sattelite HD channels vary in the amount of compression used. I think that by far the best looking DVD in my collection when displayed on my 47" Panasonic HDTV is "Gladiator" starring Russel Crowe. Particularly the arena scene where they unleash the chained tigers, etc. For more family oriented fare, try Disney's "Dinosaur", the computer animated movie that came out a few years ago.
PQ for DVD's also depends on the quality of your DVD player. This may be a silly question, but I assume you are using a 'progressive scan' DVD player? You may also want to try calibrating your TV using the "Avia" home theater calibration DVD. You can buy it at Amazon for about $40. Worth every penny.