I just watched Barefoot Gen and honestly I didn't like it a lot.
Some thoughts: it was good, but after watching Grave Of The Fireflies (which is one of my all time favorite films), it doesn't even compare.
Barefoot Gen is an anti-war film, teaching you about the history of the war and showing the horrors of war. Grave Of The Fireflies was first and foremost a human story about the delusion of independence of a child causing him to make all the wrong choices, and being a war movie was secondary. which is why its so much superior to Barefoot Gen in my opinion.