Along the same lines is Jin Roh: The Wolf Brigade. Dark, gritty and highly political, this is a unique and compelling history lesson from World War II. It also retells the tale of "Little Red Riding Hood". The anime artwork is brilliant in both mood and extraordinary detail. I wouldn't show this film to pre-teens and younger.
Another film in my collection which I think forms the counterpoint to Grave of the Fireflies is Nausicaa of the Valley of the Wind. The voice acting is excellent (Patrick Stewart is one of the mains) the anime is really well done and the film's environmental message is accessible to all ages.