My experience suggests that it is easiest to demonstrate the greater emotional pull of recorded music rendered on a superior playback system if the person already loves the music they will be hearing. To that end I always suggest that visitors bring their favorites to listening sessions. I haven't seen anyone unaffected by hearing their favorite music played back staggeringly well. The effect is automatic, like the shock of recognition. On the other hand, I've never seen a non-music lover all that impressed by great audio, regardless of what you play them.
But your point is well taken, and from years of experience I've found that most music loving audio neophytes are most impressed by relatively simple, highly melodic music with a lot of vocal content. For instance, the work of Ella Fitzgerald, Joni Mitchell, the Beatles, and, yes, Jack Johnson are all good candidates. This may have something to do with the fact that the human voice is the one that people have the most immediately available reference to.