I think Hawaii was as much of a star of Blue Hawaii as Elvis was. Most of the Elvis genre could be classified as travelogue. People back then were entertained by exotic locales in an air conditioned theatre in COLOR. Elvis was pretty much the same character in each one, different wardrobe, leading babe, backdrop, etc. They had a formula and they stuck with it. They appealed to teens but I bet he probably drew an older audience too, if they did any demographics back then. I was always impressed that the guys in the band no matter where he was knew his tunes.
I've heard that Elvis was up for the Kris Krisofferson part in "A Star is Born," but Ol' Tom wouldn't let him take the job. Too bad he never got much of a chance to be in a "real' film.
Elvis was apparently tapped to play in West Side Story but turned it down due to Col. Tom Parker convincing him to make these other movies instead. Maybe that was a blessing--I can't see him in WSS.