Do newer releases of CD's sound any better?

its a title by title experiment. the two titles you've named, have both been improved greatly.

The discs of the 80's were generally the worst (with some exceptions). Current discs in many cases are just as bad and so much of the engineering work down now days on popular music is mixed as much for MP3 performance as it is for full resolution and full frequency. This obviously is not good.

Additionally, most of todays mixes are much louder than older discs as this has too become part of the modern mixing schemes.

Jaybo is 100% correct in that it really needs to be considered on a title by title basis. Dark Side of the Moon for example has something like 8 different versions out (including SACD/DVD-A/HDCD/Redbook). I would only consider adding or replacing based on careful reviews and generally only for the music you enjoy the most. Personally, if I am too replace a Redbook with a Redbook, I want to see that it has been re-mastered versus just a new release of the same mix.

The newer Rio CD release is extremely good (sounds like I remember the Vinyl did). The Aerosmith Gold three CD box of their first three albums mastered by Doug Sax is awesome (it was originally done for SACD and is now available on CD). The Bob Ludwig remasters of the early Stones stuff is also very good. Some of the new releases of very old stuff is actaully tremendous - like how they fixed Ray Charles vocals and overdubbed with the current Count Basie band - the sound is awesome. Count Basie's Breakfast and BBQ Dance for example. Or Louis Prima's 2 disc Lounge swing album (I forget the name) is a nice addition to the collection.

Whilst rock and pop heads towards loudness and noise - there may be light at the end of the tunnel.