On a slightly different tack, ("come about!") movies are mastered quite differently from music, and have a lot more dynamic range than typical pop music, although classical recordings (and even some jazz, and certainly some of the audiophile recording folks in all genres) still preserve something close to full dynamic range.
While there are no rules for music, for movies, at least at the theatrical stage, everybody should be exactly the same loudness at "reference level" regardless of system, assuming they are calibrated properly. In music, no such concept as calibration applies. Indeed, we inherited a tendency to put levels as loud as possible (minimizes the noise level in analog recording and, frankly, takes advantage of the often nice sounding distortions that occur when you push certain tape recording devices past their linear limits). Until the last few years, the sound on our DVDs and BDs was the same as the sound for the theatrical releases, so if you could identify "reference level" in your system, you could either listen that loud or know how far you departed from it. More recently, remastering for home release has become popular, so we can never hear, or figure out, what the director/producer/sound dudes and dudettes intended to be heard in a movie theater when we play our DVDs/BDs. Frankly, handled conservatively, remastering might well be a good thing. But I kinda miss the days when I could know what the "real" mix was . . . .