Guerrila tactics will only take you so far.
If you want to really judge why the South lost the war, you need only look at what happened in the summer of 1863. On the one hand, you had Grant's move on Vicksburg. At the same time, you had Lee's move into Pennsylvania that culminated at Gettysburg.
Grant built a multi-pronged strategy, coming at Vicksburg from every direction, using both land and naval assets. He had a clear target with a strategic goal that would cripple the South if it succeeded. He threw every conceivable asset at his disposal into taking the target, and when it was over, he had wrested control of the Mississippi River from the South and cut off all supplies coming from the West.
Lee? Look, I know Lee was a strategic genius and all, but what sort of war-winning goal was there for him in rural Pennsylvania? What was there that caused him to bet the farm and go for broke? What if Lee had succeeded? What then? Let's say he'd gotten all the way to Harrisburg and even taken Harrisburg? What then? Was the North going to throw in the towel? Was Pennsylvania going to join the South? Was Lincoln going to say: "That's it guys! He's made it Harrisburg."
I remember being told in school that Lee wanted to go into Pennsylvania to gain a boot factory and get his men reshod. However, that was indicative of a huge difference between the sides. While Grant was taking strategic war-winning objectives with well-supplied forces, Lee was dealing with the basic needs of his army, trying to keep them in the field.
