the best recording with the worst system will sound better than the worst recording with the best system.
as Confucious might say....
BTW: I agree Mrtennis with you....at least to a certain point....An excellent recording however will NOT sound as good as a "judiciously compressed" recording on a mediocre system....this is why we have so much badly compressed recordings out there today and the so called "CD loudness wars". Producers & Mastering engineers know all to well what they are doing when they compress stuff for radio stations and car stereos. (They are deliberately producing something that sounds optimum on an average system. Often perceived loudness is a key criteria in defining a "good" recording for Producers who have a target market in mind; a target market dominated by owners of mediocre systems)
So what I am saying is that it is quite complex.
Those with high quality accurate systems suffer the most when listening to this badly compressed music as it is no longer optimum for their system and the music is notably compressed when compared to a good recording.
Those with poor quality systems suffer the most when listening to high quality recordings with large dynamic range, as it is no longer optimum for their system; as the listener turns up the volume to hear the "softer" sounds or detail then distortion and compression affects louder sounds and often the the balance is lost, resulting in less clarity.
In my experience, these effects are most obvious on your average movie DVD, which typically has much better dynamic range than most pop music; on mediocre systems most people will struggle to hear the dialogue until the volume is turned up rather too loud and at which point the loud parts are often distorted (this is often because the speaker cannot properly produce low level sounds accurately; these speakers that tend to have an optimum but limited sound level range or sweet spot)