This is what I think the difference you're hearing is:
- The mastering process. CD masters of pop music tend to get overly processed while the stereo mix on the DVD might not get the same processing. The mix could be the same for both coming from the mix engineer but the mix for the CD could be mastered by a different mastering engineer than PCM track on the DVD.
There are probably other factors involved as well but this is the first one that pops into my head.
Your comment about stereo vs. surround is related to how the surround mix is created. The surround mix engineer has to create a sense of environment that can sometimes make certain instruments sound weaker in order to add perspective. Who knows how much of the soundstage the engineer had to create from the tracks that he had to work with? There are plenty of audiophiles out there that would still take a good stereo recording over a surround recording in a second. It kinda goes back to that whole two ears thing... (Just kidding
)