Quality system, make poor recordings sound better?

It may not be the recording, but the mastering. At least on vinyl (I can't speak to CD or digital formats), I can play some standard reissue of an old pop album that sounds flat and lifeless; but find the right early pressing and even if the original recording has its warts and limitations, you get the breath of life in it that doesn't exist in the mediocre remaster/reissue. These differences are not subtle and involve no 'golden ears' beard stroking contemplation. The differences are pronounced and readily apparent. That then means that you have to research the best pressings, or buy a bunch of them and make that determination for yourself. I have to assume the same issue exists with CD/digital formats.
I'm at a point where I'm in it for the music, not for the sonics- but that said, I still seek out the best pressings of the music I'm interested in. It may not make as much difference for newly released material where the recording started in the digital domain, a lot of dynamic compression was used, and there isn't a wide range of options for different masterings. But, certainly for older stuff, there can literally be hundreds of different versions of a popular recording, issued at different times, from different places (both within a given country and across the world).
Some recordings just didn't start out that great to begin with, so even the best versions (on vinyl) have their limitations. I don't mind that, though I hear the shortcomings. But, there is some distance you can go to improve the source material that has nothing to do with the gear, once your system reaches a level of 'good.'

There are certainly numerous ways a recording can be of poor quality, especially with digital recordings. If the recording is suffering from excessive Dynamic Range Compression, which is very common with modern pop recordings and even remastering of older rock recordings in particular, then the damage is done and there is no "high fidelity" to be found and reproduced. These recordings typically are more enjoyable via low fidelity systems such as ipods and car stereos.

Much of todays music is engineered for inferior playback systems and not intended to be listened thru systems like the ones most of us attempt to assemble.

This is much less of an issue with Classical music and boutique labels such as Telarc, Mobile Fidelity and the like.

To Maplegorvemusic, here's an example of a poorly mastered recording: Dukes Of The Stratoshpear.
This is a remastered version done by Carolin Records, whoever they are, and is just awful. To be fair, I have never heard the original on Virgin Records so maybe this sound was intended. Never the less, it sounds terrible on a quality system, or a quality headphone setup. Maybe it would sound fine over the air on an FM radio.

Caroline was a budget imprint of Virgin if memory serves. I think some of the Bad Brains records were on that label at one point- not hi-fi, but low-fi music, cool stuff, though.

Also, one major issue I have regarding recording quality and instruments is that I am well familiar with how vocals, and instruments are suppose to sound. I played concert violin, sax, and other instruments in band and orchestra. It literally will drive me out of the room if the sound isn't close to what it is suppose to sound like. Take the recording equipment, cables, mixing boards (that included really bad circuitry), mikes, etc. and remember that all of that adds distortion, then take the compression and distortions inherent with bad Cd recordings, and the music just won't sound right. Using electronic drums, electronic instruments trying to sound like real violins, etc. and it hurts my ears. So, yes, in my opinion, I don't really care if I like the artist or not. If it is recording badly or using really terrible sounding instrumentation, I don't like listening to it. I went to a concert a little while ago at Red Rock Colorado (wonderful place) to see the Doobie (spelling) brothers and the Steve Miller Band. Each artist brought their own amplification and mikes on stage when they performed. The Doobie Brothers sounded absolutely great. But, the Steve Miller Band (who I really wanted to see/hear) sounded really terrible. It sounded muffled, heavily distorted and the sound engineer could not fix it. Several of us walked out of the venue totally disappointed. Same is true of recorded music. I don't care who it is. If it sounds bad, I either won't buy it or won't listen to it. It hurts my ears and life is too short for that. I want to enjoy my music, not sit there wondering what is wrong.

enjoy