In my humble opinion For The People is the best Strategic Civil War Game ever.
It is number one, playable. It does not get bogged down in rules minutia, and abstracts a lot of things like the Blockade, River Control, etc. While not a beer and pretzel game, it is not so complex as Mark Hermans other card driven game Empire of the Sun.
The game just really captures the feel of the CIvil War, helped much by it's card driven system which adds much flavor. The map being point to point also does a great job of simulating the logistics, and chokepoints faced by commanders at the time.
Now Victory Games Civil War used to be my favorite and is still a great game in it's own right, especially with the updated community rules. But it is a little more detailed, and not as easy to play over a few days. It really does do a great job with showing how important leaders were in battle, and showing how good corp commanders (Hood), do not necessarily make good Army commanders. Matter of fact I have hoarded 3 copies of this game I am so fond of it, and think it was the best game Victory Games put out( with NATO, and The Korean War close seconds).
The new GMT Civil War I have not played much since it's initial release. It has since gotten updated rules. Two things that bothered me were the leader effects on battles seemed very minimal. Also the strict timeline of when commanders entered and left the game, seemed like something that could be gamed out by the player. As compared to the other two games where leaders can die (rarely) in any battle they participate in. I should revisit this game, but the other two being so damned good makes it hard to find the time.