From a total war point of view, that is military + civilian, I think why the World War II era was called the greatest is because how EVERYONE fought for a common cause and everyone sacrificed for that common cause. It is also the most recent in history to have been that way. With that in mind I think World War I could be comparable.
Every one was fighting for a common cause and there was much more sacrifice in the Civil War by the civilians. The fact that both sides were "American" does not negate the great sacrifices they made in money and blood. In WWII, what part of the US, was burned to the ground like the Shenandoah Valley or Atlanta? My grand mother lived west of Savannah GA, and she still swore at Yankees. The only time I would hear her use a bad word was when she talked about Yankees. She was a couple generations removed from the war yet its affects still affected her. Hunger in the South during and after the war was very real and much worse than food rationing. Now the people in the UK really were going hungry in WWII but the US civilian population was not even close. At great cost, WWII put everyone to work so people at least had money even if they were limited in what they could buy but the Civil and Revolution war generations had limited money and even more limited items to buy. The US armed forces were very well supplied in WWII and only in a few cases was food a problem. Southern soldiers in the Civil War went hungry often as did the
I have seen the argument or questioning as to why the generation of the War Between the States (or the Civil War as some call it) couldn't be called the "Greatest Generation" just due to the number of casualties and the total civilian involvement. In my opinion it would be because we were fighting each other. It wasn't a common cause for the whole nation, whole states, counties, or even families. It was literally brother against brother in some cases.
Just because both sides were American and fighting each other does not minimize the impact of the dead and wounded that the Civil War generation suffered. Again, no comparison to the WWII generation. Not even close. Both sides were fighting for what they believed in and suffered for that cause. The south really suffered in blood and treasure and took generations to recover. After WWII, the US was the only major power without huge destruction of its civilian infrastructure. The WWII generation had it easy in that they just had to return home and return to work that did not exist prior to the war. The Civil War generation in the South had to rebuild its infrastructure as well as its population. They had no money, and in many cases, nothing left to start over with but the land.
My town has history placards about the fighting from the war. The Revolutionary War. Revolutions are just more vicious Civil Wars and the opposing sides were fighting and dying in my county. I drive by one site every day were neighbors were fighting neighbors but that is what happens in civil wars. It is far more difficult to fight your neighbors over a cause than fighting the Japanese or the Germans who attacked you and declared war on you. It is completely different to fight you neighbors over a cause or ideal. Having to fight your neighbors AND your King is one heck of a decision. There is simply no comparison to having to decide to be a traitor to your King, declare war on him, which if you loose, will likely get you executed AND have to fight your neighbors over the issue. There simply is no comparison to what the WWII generation did. None.
Can you imagine what it would be like to rebel against the US Federal government? That is what Washington and Jefferson's generation did.
The WWII generation just defended themselves, and by happenstance, what was left of the Free World. It was no small thing but no where close to what previous generations accomplished at much higher risk and cost.
Later,
Dan