How come the music from p2p programs(ares, limewire etc) has a better...

I'm not sure why you think that, but CD is definitely better quality than MP3.

Music on a CD typically takes up around 10MB per minute. MP3's are usually much less than that. It might sound better to you for one reason or another, but CD's win hands down in terms of quality.

Maybe it's what you're used to hearing, or the type of music you listen to?

it's not. quit lying to yourself. audio from a cd is uncompressed, you're hearing everything on it. assuming you're downloading mp3s, you're not getting as much. it's compressed to save space, and low and high end is cut off. music files can equal or surpass compact disc audio in quality, but the file sizes would be enormous and in a different format (.flac, .wav, .alac are common). just know that mp3s and other lossy file types certainly do not have better quality than a compact disc