Gettysburg (Marcelo, take my word, you´ll love it: Martin Sheen is an incredible Robert E. Lee and Tom Berenger is "Old Pete" Longstreet. Ted Turner himself potrays a cameo by playing George Patton´s grandfather who was killed during the Pickett´s Charge).
I didn´t know it existed, is the first time I hear of it, but don´t believe I can get it here.
A bridge too far is very good too, I have forgotten of it.
Regarding Private Ryan, I really hate Spielberger, but I must admit that he did it with this film. Historically or technically you will sure learn very little from a war movie, so I like just to see what an actual combat looks like from the soldier point of view, and here Private Ryan excels. Soldiers don´t just receive a bullet and fall dead to the ground unaware of what had happened, like in Combat TV series, but most times they are just wounded and follows a long agony. And the only movie I have seen to show this misery so real is this one.