You say different but is it better? The hyper-compression that is found on so many of today's recordings would be my initial guess without additional information as recordingpro indicated. Remember this will move the RMS of the recording much higher than yours and if you don't level match it can be easy to be fooled that the loud one is 'better'. It rarely is.
Aside from that, it could be many factors. Do the CDs you like sound fuller? more spacious? interesting effects? clearer? Take one aspect that you like from those CDs and work at getting your own to sound that way. Once you are close move on to something else. After some time and experimentation you will learn what can help and what doesn't.
Kevin S. Mucha
Coerce Recording Services