Years from now, if Mark Christopher's timid, meandering film "54" is spoken of at all, it will probably be lumped together with Whit Stillman's "Last Days of Disco" as one of two movies released in 1998 to bungle the same opportunity. Both films, while purporting to examine New York City's voracious late-1970s disco culture, adopt a primly distanced attitude toward a moment, just before the AIDS epidemic struck, when voluptuous hedonism became a kind of mass hysteria. Sex, drugs and disco: you couldn't ask for a juicier mix. But when it comes to squeezing juice, both movies come up dry.