Zulu was a great war film. It had fantastic battle sequences, and made the British soldiers appropriately heroic without dismissing the courage and grace of their Zulu enemy.
They Died with their Boots On is one of the worst, because of it's ridiculous portrayal of Custer as a brash, fun-loving, well-meaning rake who was the last man standing at the Last Stand, finally dropping after being shot about thirty times. I don't go the whole hog on the racist Indian-hating monster view of Custer, but he should have been depicted as the rather knuckle-headed, careless, self-important, and brave character he really was.