Flags of Our Fathers certainly wasn't the war movie of our fathers. Battlefield gore is a necessary ingredient in any war movie of our time, as well as soldiers' profanity, and understandably so. My own preference in historical fiction runs to verisimilitude, but that isn't to say that I didn't like The Sands of Iwo Jima. (And didn't realize, until I looked it up recently, that the three surviving flag raisers on Mount Suribachi appeared as themselves in that movie.)
Interestingly, the most effective horror-of-war scene in Flags involved off-screen gore. At one point, one of the men (Iggy) goes mysteriously missing from the hillside. Later, his comrades discover that the Japanese pulled him into one of their caves and killed him in a way the American soldier who found him would only describe as, "look what they did to the poor son of a bitch." At that point one of the characters is looking at whatever remains of Iggy, but we don't see it, and it's much more horrible that way.
On the whole, Flags was a worthwhile effort, but it suffered from a jumpy flashback structure and an unnecessary framing device, especially the interview scenes in which some of the old soldiers tell us all What It Means, to establish the movie's stance as a hero-myth-buster. Fine. Bust that hero myth. It's tiresome, though, because movies have been bravely busting the myth for 40 years now.
A straightforward narrative would have been better: the landing, the flag raisings, the deaths of some of the men involved, the nation's reaction to the iconic photo, the survivors on the bond tour, their essentially unhappy experiences after the war (especially Ira Hayes) -- it could have all been chronological without jumping or modern commentary. Then the audience could have made their own conclusions about the story.
Also of interest: lately the Japanese have started using the prewar name for the island. It's their island, and they can call it what they want. But it also belongs to the history of this country, and it should be Iwo Jima as long as histories are being written in English.