I like this movie. I have studied the period of the crusades for a long time. The film has a number of ahistorical aspects, but Ridley Scott is a great director and I think he "pulls it off."
The film gives the impression that the Kingdom of Jerusalem pretty much consisted of Jerusalem. In fact, it reached from Ghaza to Beirut and from the Mediterranean to the desert in Trans-Jordan.
The film gives the impression that the kingdom ended with the fall of Jerusalem to Saladin in 1187 AD. In fact, the kingdom revived and lasted nearly a hundred more years.
The Templars were nothing like their image in the film. they were quite sophisticated in their relations with Muslims. A Muslim chronicler of the time wrote that during his visits to Jerusalem he stayed at their guest house and they made a place in one of their churches for him to pray. Guy de Lusignan and Reynald de Chatillon had nothing to do with the Templars. The Templars were exactly like the Hospitallers who were portrayed in a favorable light in the film.
Saladin's behavior at Jerusalem was admirable, but on other fields, (Acre and Hittin) he killed thousands of prisoners.
A realistic portrayal of the actual nature of Muslim/Christian relations in the Latin kingdom in the time of Baldwin the IV.
A richness of detail in costuming and atmosphere which brings the period to life.
A history lesson. Many need it.