Quality system, make poor recordings sound better?

Do the poor ones really sound worse or just worse in comparison to how good the good stuff sounds?

AN improvement is an improvement. It can only make things better, though some way more than others perhaps.

I notice that as I move up the audio chain, poor CD recordings sound worse and the good ones sound superb, should this be the case?

Yes, this is normal. Increased resolution is a double edged sword. Think of it as putting a clearer window in your home. Your view may be better or worse depending on the view outside the window.

Also I on any given day my system sounds different even with the same CDs. Any thoughts on this as well?

This probably has to do with your power. Many notice it will even sound different at different times during the day. Usually the system will sound better when overall electrical usage is lower, on evenings and weekends.

Cheers,
John

With respect to your first question, to me it depends on what you mean by "moving up the audio chain". If you're moving up to more and more "revealing" components, or perhaps to wires that might emphasize certain parts of the frequency spectrum, particularly the higher frequencies, then yes, what you're describing can happen. Another upgrade path, though, that I now (after having gone the other way) try to follow is to make sure that you can listen to and enjoy most of your music collection with the new components, and I believe that this can be done while still maintaining high sound quality and even improving it. There are components out there that can let you listen to and enjoy lower-resolution sources like internet radio while still letting great recordings shine. I think this is what people are thinking of when they refer to "musical" components.

With respect to your second observation, there are a lot of factors that can cause this, both related to your system (power not quite up to optimum levels, wear of tubes, etc.) and related to you and your mood. With respect to the former, a really good power conditioner or regenerator, or listening to your system late at night when demands on the power grid are lower, can lessen those differences attributable to "dirty" power coming into your home. But I find that my mood and concentration level when listening vary a lot, and that can definitely affect the way I respond to the same recordings.

I have found just the opposite . The more my system gets dialed in the better all recordings are . I listen strictly to digital . Right now 90% of songs sound fantastic . Last winter i would skip through my playlist looking for the best recordings , A slave to an improperly amplified set of speakers. Proper amps for my speakers and a few other changes made a night and day difference . Something in your system is not jiving , could be room , speaker placement , mismatch of components ,ect... It is not the recordings that are poor . Obviouosly some are better than others . But no recording done for a major record label should sound terrible ,regardless of format .

Maplegrovemusic,
My experience is the same as you described. As my system has evolved, poor or average sounding recordings have clearly improved (hearing/appreciating more of the music's expression/emotion). The better recordings just became more so.