After seeing couple of certified THX DVDs, the answer to the question would be maybe yes or no.

THX certified DVDs Terminator 2 (2 disc special edition) and What Dreams May Come are the two that I own, and video quality on these DVDs is not the greatest. I seen better video on non THX DVDs. I don’t know how to describe it correctly, but the problem I see with THX DVDs are slight graininess, and lack of “warmth”. The picture have sanitized look that is flat and non dimensional.

May be I should look at few more THX DVDs to be more conclusive