Now that I've heard SACDs played with their DSD resolution, I would rank the media as follows:
SACD
DVD or Blu-Ray
HDCD
CD
This is based on playing them all through the same transport and DAC. So, basically, the higher the resolution, the better the sound if you're listening to the same recording. Before I heard SACDs in DSD, I wasn't impressed with SACDs that were converted to 24/192 PCM.
The difference I hear is that higher-res sounds more analog--smoother with less digital glare or shrillness.
Now, there are some CDs that were very well-recorded that can sound comparable to higher-res media of other recordings, but they are in the minority, in my experience--mostly audiophile labels like Chesky, Bainbridge, Telarc.