The best MP3's are the ones you make yourself. T o make MP3 files you will need two types of programs. One is a CD-Ripper. The other is a MP3 encoding program.
Some programs offer both in one package.
A good CD-Ripper will produce a digitally perfect copy of the music. Most CD-Rippers will output a .wav file. The second step is to encode this .wav file with a MP3 encoder. If the two programs are combined in one, then your job is all the easier. However, if you use a sepearate program to encode, don't forget to delete the .wav file after encoding.