I am going to look at this from a technical standpoint. First, I still have a record player, and even though DSP on CD players has gotten really good in the recent years, Many CD's by default have an un-natural "tinny" sound to them without the DSP processing.
Second, since digital recordings use bits, and are not a continuous like analog recordings, bit rate makes a difference in the quality when listening to MP3's
a MP3 recorded at 320 Kbit/s, while it may sound good, really is not what would be called a high quality digital recording. And this junk that ITunes, and other online stores are selling for $0.99 per song for a 96 Kbit or 128kit mp3 is a rip off. It shows how naive people really are.
People want mp3's to save space over conventional wav files or other lossless formats. If an mp3 is to have the full quality of a cd, then each track will be 40-100mb each and have a bit rate of 640 Kbit/s or 1280Kbit/s and you will need a 1000mb (1TB) mp3 player to have any sort of mp3 collection.
I am actually waiting for Blu Ray Audio Disc's with 7 or 10 channel audio at super high bit rates, they are around the corner, and the RIAA will institute their typical price fixing as they did with CD's.