After seeing Prometheus, I figured I'd finally get around to checking this one out (in the DVD director's cut).
The cinematography and composition alone is worth it. The overall impression is Jean-Leon Gerome (the clinical Orientalist), mixed with some Georges de La Tour (the pensive Baroque candlelight painter).
I've noticed that during falling-crime times, exoticism goes for a more ethnographic, clinical, documentarian, touristic approach, like Gerome during the Victorian era, the Jimmy Stewart version of The Man Who Knew Too Much during the mid-century, and... well, I didn't know quite what the example would be from the last 20 years, but now I've got one.
In rising-crime times, exoticism turns more toward the subjective, supernatural, stepping-into-a-different-dimension approach, such as just about every gothic novel from the Romantic-Gothic period, the Douglas Fairbanks version of The Thief of Bagdad from the Jazz Age, and the Indiana Jones movies from the New Wave Age.
In Kingdom of Heaven, the supernatural part of religion is entirely absent; instead it's shown as a social-political means of holding together a faction or larger group. We assume that there is some supernatural element to the beliefs that hold them together, but the focus of the movie is just on the social scientific fact that it does hold them together.
There's some pretty good basic ethnography of pastoralist people, like their obsession with honor, reciprocity (both an eye-for-an-eye as well as kindness repaying kindness), and the sanctity of guest-host relations. Too bad they didn't show any livestock, though -- their subsistence is shown to be irrigated agriculture in a desert. Perhaps they felt that showing herds of sheep, goats, and cattle would've lent too romantic or idyllic of an air to the place, even if it would've been more authentic.
Combat scenes were the same unthrilling stuff I've come to expect, but it wasn't primarily a war movie, so that's not a big deal.
The one major historical inaccuracy that actually does affect how it should have been written and shot is the zeitgeist of circa 1200 AD. That was during the Medieval Warm Period, when it was hot enough that the Vikings could sail iceless seas toward a then-habitable Greenland. Warmer weather invariably makes people more restless and hot-tempered, as seen by the surging popularity then of young dudes wandering off toward Jerusalem to do battle against the Muslims. That was also around the height of the Troubadour and courtly love culture, full of fun-loving men and boy-crazy girls.
Only a bit of that comes through in Kingdom of Heaven, which opens up in what looks more like the Little Ice Age, and continues to show relatively cool-headed and passion-delaying main characters throughout. Queen Sibylla in particular comes off as far less excitable and fiery-blooded than a young woman would've been back then. (Whether or not the real-life Queen was this way doesn't matter, since they already chose to fictionalize her story.) She's played more like a stereotypically frigid JAP.
For a better look at what the time and place probably felt like, check out The Canterbury Tales and The Decameron by Pier Paolo Pasolini. They depict the later 1300s, but the zeitgeist then was similar enough to the late 1100s -- hotter, rowdier, and bawdier than what we think of as Ye Olden Times. Since the look and feel of the movie is clearly the high point of the experience, they should have chosen a story from a time and place more suitable to the reflective and clinical aesthetic.