It is very hard for a new piece to suddenly become "the new classic" especially after piece like Romance and Recuerdos have been around forever. 
Cavatina was part of the music track of a TV series and composer Stanley Myers developed it into a full piece under the insistence of Australian guitarist John Williams. It later became the soundtrack of award winning movie the "deer hunter", a Vietnam saga with a  great cast of actors including Robert de Niro, Maryl Streep and Christopher Walken. John Williams later performed it in  duo (with orchestral accompaniment) with singer Cleo Lane.

Just like with every great thing in life, simplicity is at the base. Melodically and harmonically Cavatina is simply straightforward and it reaches climaxes in a gentle though powerful way. Technically, Cavatina is very challenging. The solo guitar tries to reproduce the guitar duo performed by Williams in the movie soundtrack version. Keeping the melody separated and at the same time very much bonded and dealing with the long succession of barres throughout different sections of the piece, calls for a not less than perfect fingering and the correct use of the playing apparatus. 

Cavatina's main technical challenge is the long succession of barres which, besides presenting difficulties of their own, pose the extra bonus of having to produce a smooth sounding melody. Achieving all this while intense force is applied to the left hand is a conquest. 

This is one of the few guitar pieces I wanted to play from the first moment I heard it.  Hear Cavatina