At the time of the Mahdi, the Sudanese people, who were predominantly Muslim in the part of the Sudan where this historical drama occurred, were oppressed by a foreign Egyptian government, whichg was directed by a corrupt and brutal Ottoman Empire. The British supported the Ottoman Port and Egypt in oppressing the Sudanese as it aided their imperial goals. The Mahdi, the son of a Sudanese boat-builder, attempted to overthrow the corrupt Turkish domination of the Sudan and their English and Egyptian puppets, and he succeeded.
"Chinese" Charles Gordon, a man in many ways a Christian mirror of the Mahdi, became involved by convoluted means in the situation and, as one historian put it, attempted to defend the iundefensible at Khartoum.
The Mahdi actually admired Gordon, attempted to convert him, entered into a correspondence with him over religious matters, and ordered his troops to capture Gordon alive as he - the Mahdi- believed Gordon was a good man fighting in a bad cause and he wished to spare his life. The Mahdi was enraged when he learned that his troops had cut down Gordon, although, knowing the personality of Gordon, capturing him alive would have been an expensive proposition.
Much later, after the death of the Mahdi, even European troops were impressed by the unbelievable courage of his followers at Omdurman when they heroically and recklessly charged into modern European artillery and machine gun fire armed mainly with spears and swords, and died to the last man.
In the big picture, the Mahdi and Gordon were both good and brave men. Osama Bin Laddin, killer of women, children and old men, is a vile monster by any same man's standards in any age.
I have not seen the picture, but would like to. Heston is a great actor and another great man. But I doubt that Hollywood did credit to the complicated personality of Gordon or the Mahdi.