2 channel redbook audio cd if mastered properly will sound better than DD or DTS anyday for the simple reason that both DTS and DD use lossy compressions.The test that you did proves any of the following:
1.Your audio setup is better for movies than stereo.
2.Some audio cds are mastered very badly.There is a chance that the newer DTS or DD version could have done a better job.THIS DOES NOT PROVE THAT DD OR DTS FORMAT IS BETTER.