This may not be a direct answer to the OP, but when I am driving - AM Radio is easier on my ears and I can listen to it longer and with less fatigue than I can an FM station, XM, wife, CD's, iPod, etc...
 
Back to the OP....
For the most part recordings match the equipment (quality) of that period because that is what it was prepared for. If you listen to an original Glen Miller recording on a 78 it is magical compared to listening to it on re-released CD through a modern hi-fi system. BUT - if you listen to "In the Digital Mood" (a modern era of the orchestra recording in digital, for a CD release) it's amazing on CD. Same songs, same parts - played equally as well (arguably better).
 
Just my 2 cents.
 

Rain
.... to me, the sweetest sounding pop music was released in the mid-late 70's.

 
I couldn't agree more.... There is timeless music from all decades, but the 70's rule the "classic" airwaves for a reason. I'm convinced it's a combination of great artists, great songs and great production. And in all three phases, nobody sounded like anyone else.

Beepster
My opinion... it's the fact all our new fangled gear is over accentuating the bass on everything to placate the dance/hip hop pop crud that's infected the industry.
 
Don't get me wrong... I love GOOD dance and GOOD hip hop and like listening to it through a system capable of ball rattling, bowel churning epicness.... but that low rumble is a relatively new thing in audio production (and the playback equipment).
 
Turn off your sub woofer or put it through a system that is era consistent and I bet it'll sound way better.
 
 
In fact... could you tell my neighbors to turn off their sub woofers while you're at it? Fookin' things should be banned in apartment buildings. lol...
 
 
Of course you've likely got flat freq monitors/headphones too which would probably get rid of that low end crap naturally but also accentuate the flaws in the recordings of the time (which would sound better through a stereo system of the time).
 
I know you've got a VRM Box and maybe this is a stupid suggestion (but I've been tempted to try it myself) is run your monitors out of it (with a Y splitter) to get the speaker emulation. Of course you get the room emu too which would likely ruin the whole thing but yanno... simulated speakers anyway.
 
Really though I think all new equipment should have "I'm listening to ball rattling modern dance stuff" and "I'm listening to ANYTHING else" settings.
 
That sub bass shiz started in dance halls where you couldn't hear anything else except the rattling sub bass. Now it's expected to be in our homes (and pissing off our cranky old neighbors). Now EVERYTHING has to be mixed that way and it's annoying.
 
Meh.
 
Hi, sharke. ;-)

 
Hi Beepster, 
 
I agree with you about the overdone bass in much of today's music. For some genres it's obviously quite appropriate and not exactly a new thing - look at reggae. Mind you, even back in the days of Bob Marley they were pretty much restricted by how much bass they could carve into a vinyl record without the needle jumping out. No such limitations with digital and as such bass has gone through the roof. 
 
Don't get me wrong, I love some bass heavy music. As you may know I have a healthy love of (good quality) electronica, and sometimes the in your face bass is sublime. There is something about sub bass that takes you into another world, especially when the frequencies are so low that you feel them more than hear them, yet you can still "feel" the pitch of the notes. Done well and heard on a system that can reproduce it, you will be affected in an almost ancient, tribal kind of way. Sub bass frequencies can be profound if used properly. 
 
But I cannot stand these modern remasterings of old music where it sounds like all they've done is crank the bass up. One example I always use is Talking Heads' "Born Under Punches," one of my all time favorite tracks. I love the sound of those early Talking Heads records - they were such open, airy mixes and balanced perfectly IMO. The bass guitar is bright and funky sounding with a lot of high end and just sits perfectly in the track. Cut to the 2005 remastered version and they appear to have tried to simulate how it would sound if played through Beats headphones, i.e. an overblown low end. So unnecessary and ruins the original mix. 
 
I think some have missed the point here though. It's not that these old tracks were mixed so that they only sound good on cheap equipment. I can still appreciate that it's a good mix, and of course hi-fidelity equipment is certainly nothing new. It's just that I enjoy it better through AM radio for some reason. Mind you, this doesn't apply to all old music. I'd much rather listen to Steely Dan, Miles Davis or the Mahavishnu Orchestra on top quality gear. It's more the old classic top 40 hits that I enjoy better through the radio. 

I was helping a friend with something at his house and pretty much singing along to all the songs being played on the radio, then the station identification came on and I found it was considered an "Oldies" station...  My good mood died about then. *Sigh...* 

Well...I keep hoping but with just a few exceptions older is still better. By almost any yardstick except, perhaps, production values. And, really, even by that delineator. I mean when ol Blue Eyes recorded with a full orchestra they all had to play and perform it perfectly from start to finish. And then the engineers had to record it perfectly and mix and master it perfectly...all with the tools on hand in the 40s, 50s and 60s. And those records still stand the test of time. Sheesh.

1969-Abbey Road is still my favorite sounding album of all time. 1973- Darkside of the moon still sounds great. Both Recorded at Abbey Road. Muscle Shoals had two studios and both had great sounding albums made there. Of course there are a thousand examples (good recordings have been being made in world class studios for a long time). This reminds me of the conversation about how many people actually use tape sims. I think this 70's sound is being searched for by many. Others embrace the clean sound of digital. I think it's simply easier to over do (or abuse) recordings these days.

yorolpal
Well...I keep hoping but with just a few exceptions older is still better. By almost any yardstick except, perhaps, production values. And, really, even by that delineator. I mean when ol Blue Eyes recorded with a full orchestra they all had to play and perform it perfectly from start to finish. And then the engineers had to record it perfectly and mix and master it perfectly...all with the tools on hand in the 40s, 50s and 60s. And those records still stand the test of time. Sheesh.

Years ago I read an interview in an audiophile magazine with a guy who had this incredible setup in his basement, and he stated very firmly that by far and away the best recordings he had ever heard were the BBC's Last Night Of The Proms from the 1950's. 

People can try and make everything sound as huge and powerful as possible, adding every possible combination of compression and reverb and EQ, I've yet to hear anything that sounds as loud and mean as the snare on the opening cut on Elvis Christmas record. Or those old Sun records. Same for the first few Beatles albums. 
 
And what about that iconic fill at the beginning of Led Zep Dyer Maker?
 
The secret - the space around the sound. You have a reference as to just how loud it must be because there's so much room around it that it stands out.
 
That's the biggest problem I have with modern music - I feel unwelcome in it. There's no room for the listener whatsoever. I feel like the singer is singing an inch from my face, and I have all the band clinging to me and I just want them to let go of me. It truly is an assault. 
 
You can't have it both way - either it punches or it pumps/sucks. 
 
I remember listening to Sgt Pepper with headphones and feeling like I was in the room with them - there are so many places to stand, so many possible perspectives on what's happening. 
 
Figuratively speaking, 50s and 60s music sound a bit 2D, late 60's and 70's sound 3D, and 80's too I guess. 
 
But modern music is Zero D. It's a flat line, dry and rigid.
And then, obviously there's the music itself.

"older is better"
 
My hypothesis - because it's been ingrained in us after EONS of listening to it.

Hi,
 
NP:
 
"let's take a trip down whittier boulevard .... " and here comes Bapu on the bass!
 
We'll have to follow this up with The Clams ... version of "Close to You"
 
Very weird ... so you think that listening to a song about yellow polka dot bikini ... is better on ... than ... ???
 
I wanna go to the bathroom, and pull a Ron Geesin/Roger Waters!