Song That Started It 2

Hmmm. Not sure I understand the question but if it is what I think it is then often times the first album of a band is their best because it´s fresh and they don´t fall into rehashing stuff for the next albums.
 
Quiet Riot went downhill fast after "Metal Health."
I think Def Lep peaked with both High and Dry" and "Pyromania" as I felt both were equal, but they went downhill after that as well.
"Balls to the Wall" made Accept a household name for a very short time, but I thought "Metal Heart" (their following release) was their peak.
"Rainbow in the Dark" was DIo's biggest hit, but I think "Holy Diver" and "The Last in Line" were pretty equal.
Ozzy era Sabbath was the most famous, but I think their best release cover to cover was "Heaven and Hell" with Ronnie. Only "Wishing Well" was a "filler" song. in fact, "The Mob Rules" was pretty good too.
"Heaven Tonight" made Yngwie commercially acceptable, but commercial or not, it was easily YM's best work (non-instrumental.) JLT and YM were made to be together.
Guns and Roses were overrated from the start but put out a bunch of shit after AfD.
Tesla's "The Great Radio Contreversy" was their biggest seller, but "Mechanical Resonance" (their first) was incredible.


Bryant
 
I think it takes years for a band to come up with a mature songwriting and its own sound.
Thus I don't think bands like Queensryche, Judas Priest, Metallica, etc., peaked with their debut album, because their major influences were still predominant.

Sometimes it can be the case for bands who were already around for years and years (Helloween, Exodus), but I'm not the kind of tr00 guy who always tell that "their first rehearsal demo ruled, everything else sucked" ;)
 
I think it´s much about nostalgia but also because after a few albums a band might want to change their sound and then people dont think it sounds like it "should" sound.