DTS/DD vs. CD Audio quality-opinions?

[kexodusc]

Three of my friends and I performed a little test this weekend, comparing 5 albums of various music types. We used my friend's setup: a Yamaha RX-V1400, with Paradigm speakers - 6 Studio 20's, a PW-2100 and the CC-470 for playback. Older Yamaha CD player and Panasonic DVD player were used. The goal was to determine if DD/DTS audio tracks sounded better than CD audio.
Here's what we collectively came up with:
Metallica (Black Album) - Definitely better in DD than CD audio in stereo
Diana Krall - Live in Paris - Again, DTS better than the CD audio version
Pink Floyd - Dark Side of the Moon - 5.1 DD has won the test already.
Neal Young - Harvest - Don't know if it was the recording or what, but 2-channel stereo won out over 5.1 audio
The Eagles - Hell Freezes Over - 3 votes to 1 in favour of DTS over CD Audio.

Now, is there some technical information I can use to support the results of this admittedly subjective test? Is it bit rate/sec, sampling rates, 16 vs. 24 bit "word length"? Or do we just subjectively prefer the added ambience a 5.1 music source delivers?
Any comments?