At its core this is a romance, boy meets girl, both dream of stardom. Adapted from a musical that makes “Mama Mia” look sophisticated Rock of Ages pleasure comes from the larger than life characters surrounding our rather uninspiring young couple. Silly to the point of puerile, almost plot less and everyone sings to boot. Rock of Ages is the definition, thanks to a cast that includes Giamatti and Baldwin, of ‘guilty pleasure’.