Remasters - are they better? What exactly is it?

In my opinion, many here have hit on it.  Much of what was recorded back in day, as far as popular music, was recorded where much of the highs and specially the lows, were rolled off, because in general most buyers didn’t have the capacity to reproduce the sounds rolled off, so why put them on the recording.  If the master tapes have the content, then the remaster process can add, what was not on the original commercial recording.
As some said, Desperado and Crime Of The Century are indeed quality recordings made back in the day.  Classical music, as well as some jazz, didn’t suffer from engineers rolling off the frequencies, in most cases.

@jaybe 

Oh I know. My post was a little tongue in cheek

Over the last twenty years or so a lot of pop/rock music has increasingly been mastered for play on car stereos, mobile devices, and earbuds.

A lot of content today is reduced bitrate. OTA radio stations 'rip' material to MP3 for smaller storage. For a visual on how bit-rate reduction distorts the music, see http://ielogical.com/Lossy/ 

Those of us who insist on listening to music on a quality system are probably now in the minority.

No probability about it. We always have been and likely always will.

Sadly, the great unwashed think they have a quality system, but it can be egregious. More than once, I've asked that a system be stopped or I shall have to leave. I literally become nauseous from the swirling dervishes caused by bitrate reduction. I stream reduced bitrate, but playback is mono.

A "remaster" can sound better, worse or the same as an original pressing.  There are too many variables in play to give a blanket answer.

Some remasters of vintage/golden age material sound better.  Back in the day, engineers had to be mindful of the (low) quality of home listening equipment.  Unfortunately this often led to compression and truncated frequency extremes.  Example:  Verve was forced to reissue many classic titles because 1st pressing were too dynamic for most home systems.  Later issues even during the Gold Age sound inferior as a result.  It is only with the beginning of true high end remasters starting in the 70's that listeners could hear what was actually on the master tape.  RCA Living Stereo LPs from the 50's-60's were engineered to sound great on home equipment- because EQ was applied during the mastering process.  The first series of Classic Records RCA reissues cut directly from the master tape with very little EQ or change.  Listeners were unhappy because they did not hear "better" versions of what they were intimately familiar with !  What they received was actually closer to the master tape, but we deemed inferior !   Classic incorporated some of the original EQ in subsequent reissues.   

Some remasters sound worse.  Many MSFL and other premium remasters sound different (and worse to many) because the remastering engineers applied EQ adjustments.  Some sound brittle or booming, some have muddled vocals, some sound like a "smiley face".   

The best remasters tend to occur when an engineer carefully listens to an original pressing to determine how it was produced, then approaches the master tape from a the perspective of recreating a better version of the original.   Example:  Beatles in Mono.  The engineers and producers used mint first pressings as their reference.  Some of the resulting mono LPs sound -better- than original YB Parlophone pressings, and the remainder sound just as good.

We are now at the point where even RnR masters are 45-50yrs old, and suffered from indifferent storage quality, and multiple playback on machines of varying quality such that the tape has noticeably deteriorated.   Rather than risk further damage and to reduce costs, labels are transferring master tapes to digital files.  Many were converted at 16/44 during the 80's and 90's, then the master tape was discarded because digital is "forever".  It is only in the past 10yrs that we see many labels choosing a higher resolution level for digital conversion.  Most labels use something between 16/48 and 24/192, with the sweet spot being 24/88 or 24/96.  The resulting digital master is then used to create new CDs, streaming content, and to generate mothers for LP pressings.   Digital masters are much cheaper to administer- send bits by secure line versus shipping a master tape....    Contrary to industry spin, you CAN hear a difference between a fully analogue LP remastered pressing and an LP pressing with digital somewhere in the production chain.   Don't be fooled by claims of "from the master tapes"  or anything similar because a DIGITAL conversion is actually taken from the original master tapes as a source !  

Awesome info from everyone.  For those whom I disagree'd with, I'm mainly just playing devil's advocate.

Like I wish so badly that Elvis's old stuff was a little more "oomphy".. NOT electronica hip hop fakery, but just more "crank up-ability" (im struggling for words here).

Here's an example..  Elton John "Don't Let the Sun Go Down on Me"....

Original recording: ehhh boring, not going to make me stand up and clap. But his newer live versions at Madison Square Garden, ohhhh yeah... It gets my adrenaline pumping.

Here's a better example yall are going to kill me for.

"The Weight" by The Band sounds bland and uninvolving compared to Marty Stuarts newer version which I actually like alot better.