I'll give you some specifics, for Charlton and the others.
Fightin' Army #76-80, 82-92 "The Lonely War of Captain Willy Schultz.
Willy Schultz is a first generation American, whose parents came from Germany, serving in North Africa. He is framed for murder, after an ambush and court martialled. he escapes into the desert and is forced to hide out in german uniform, with an Afrika Korps panzer unit. He has to try to stay alive, yet not harm Allied soldiers. In later stories, he gets back to the Allied side and there are switches of him in German uniform and Allied, with him also aiding partisans. The series was written by Will Franz and drawn by Sam Glanzman. It is a mature series that gets into the real horror of war and the comradery between soldiers, the fight to stay alive and keep your buddies alive, as that matters more than the reasons behind the war. When Roger Broughton bought the property, he reprinted some of it in black & white comics, under his ACG label. He also commossioned and ending to the story, from Franz and Glanzman, but never published it.
Fightin' Marines #78-108, Shotgun Harker and Chicken.
Set in Vietnam, with Marine sgt Harker, who uses a shotgun (actually very common, for jungle fighting, often carried by the point man on Marine patrols) and PFC "Chicken" Smith. Smith represented more of a counter culture figure, with flowers in his helmet; but, was not a coward. He and Harker had some great stories, from the prolific Joe Gill.
Army War Heroes #22-37, The Iron Corporal
Another from Will Franz and Sam Glanzman, about an American serving with the Australian Army, in the Pacific.
War Heroes #27; Fightin' Army #79, 82, 83-The Devil's Brigade.
Another from Franz and Glanzman, about a unit, similar to the British LRDG, fighting in North Africa.
Will Franz was a young man, who had struck up a correspondence with Sam Glanzman, over the war comics. he was a history buff, with great reference material; mostly, from Glanzman's comics. He started selling scripts to Charlton and Glanzman drew many of them. Glanzman made it look authentic, while Franz gave it a maturity not seen often, in comics.
Combat #1-40, Dell/Western
These are fantastic comics, from Dell/Western, with story and art from Sam Glanzman, covering actual battles of the war, before morphing into a more standard war comic. John F Kennedy and PT 109 are featured in issue 4.
Sam Glanzman is a name you will hear constantly, from me. He was a Navy veteran, who served on the USS Stevens, in the Pacific. He was also an established artist, in the 40s, aiding his brother David. He left art behind, after the war; but came back to it, working for Dell and Charlton, before working steadily for DC and Marvel. He is best known for his USS Stevens stories, in Our Army at War.
The listing of stories can be found here. The USS Stevens stories were slightly fictionalized accounts of Glanzman's experiences or those that happened elsewhere, in the Pacific. The entirety was collected by Dover, a few years ago.
Glanzman also had a run on GI Combat, handling The Haunted Tank, through issue #287.
Glanzman also wrote and drew his memoirs, A Sailor's Story, in the Marvel Graphic Novel line (2 volumes), which were later collected into a single volume, by Dover.
The Kubert and Kanigher team on Enemy Ace is a must-read, as are the Kubert and Russ Heath Sgt Rock stories, from Our Army at War. M'lle Marie, from Star spangled War, is another great one, about a female member of the French Maquis (the Resistance).
The first year of Sgt Fury has great Kirby art and is worth reading; but, Dick Ayers became the long running artist on it, after. The Roy Thomas years have some great stories, some swiped from movies. When John Severin joins on art and Gary Friedrich is writing, it is on par with the DC books, in terms of story quality. They did a lot of reprints, though.
Charlton's Attack was a later one, but with plenty of great stories.
Charlton had Fightin' Army, Fightin' Marines, Fightin' Air Force, (Argumentative Coast Guard, Dancin' USO, Scufflin' Boy Scouts.....
) Army War Heroes, Marine War Heroes, War Heroes, Attack!, War.
The EC books are great, DC's are golden. GI Combat was actually a Quality Comics title, acquired when DC bought their line. DC's Our Army at War, Star Spangled War, and Sgt Rock and the Unknown Soldier are filled with some of DC's best stories.
For later era stuff, anything by Wayne Vansant is great, such as Battlegroup Peiper, from Caliber, and his work on the early part of the war in th Pacific, from Apple (Days of Darkness and Days of Wrath). Vansant gets his history right.