Why are Elvis Presley's Sun recordings considered to be more important than his RCA recordings? ?

They were much like the spate of "Unplugged" albums that were popular about 30 yrs. ago: raw, almost live.  Usually quickly recorded in only a few takes with few, if any overdubs by just a handful of people.  They worked in a small & primitive studio with very basic equipment.  Also, he was younger, hungrier for the fame that, when it came, almost overwhelmed him.  He was less well-known, a LOT poorer.  He wasn't idolised, jaded or with an inflated head.  He wasn't simply going through the motions, as he clearly did on a lot of his later work.       

P.S.: "Sad (lovely) Eyed ...:"  He didn't join the army.  He was conscripted.  I doubt that he truly wanted to pause his career in mid-blossom.  He was never as good after that.  

Assuming that's true, in the world of collecting, earlier is almost always better. The rookie card, first 45 record etc. include intrinsic value added. Early Elvis is Sun records. Collectibles follow simple supply/demand economics.

BECAUSE OF AUTHENTICITY

They just have a raw spontinaeity that Elvis lost after he became famous, particluarly after he joined the army and during the RCA years his songs were being chosen for him and his albums were just full of session musicians.

i dont think thats true