All of Stanley Kubrick’s features look better now than when they were first released, but Barry Lyndon, which fared poorly at the box office in 1975, remains his most underrated. It may also be his greatest. This personal, idiosyncratic, melancholy, and long (three hours) adaptation of the Thackeray novel is exquisitely shot in natural light (or, in night scenes, candlelight) by John Alcott, with frequent use of slow backward zooms that distance us, both historically and emotionally, from its rambling picaresque narrative about an 18th-century Irish upstart (Ryan O’Neal). Despite its ponderous, funereal moods and pacing, the film is a highly accomplished piece of storytelling, building to one of the most suspenseful duels ever staged. It also repays close attention as a complex and fascinating historical meditation, as enigmatic in its way as 2001: A Space Odyssey. With Marisa Berenson, Patrick Magee, Hardy Kruger, and Leonard Rossiter; narrated by Michael Hordern. PG, 183 min. (JR)