Off the cuff, I'd say, Schlondorff's "The Tin Drum". Possibly my absolute adoration of Grass' novel is to blame, but I thought the film failed to deliver on many levels. First, it turns Oscar into this hideous, monstrous child and you simply want to slap him, while the Oscar of the novel elicits your sympathies while he continues to do the most outrageous things. The screams and the drumming are very unimaginative on a cinematic level. What works brilliantly in the written form does not necessarily translate into good cinema. The crux of the problem is that the film deals with Oscar's story in a realist mode and lacks the breadth, the magic and the mythic qualities of Grass's vision.