Rock of Ages is a movie adaptation of a Broadway jukebox musical dedicated largely to hair-band hits of the 1980s. Whitesnake? Twisted Sister? Bon Jovi? What sort of Hell-brew might we have here? Yet somehow, against all disinclination, writes Kurt Loder, it begins to stir your interest. Tom Cruise in particular, with his chest full of tattoos, his pet baboon (who doubles as a bartender), and his odd jeweled codpiece, is very entertaining.