I'm trying to think of mass-appeal war stories with a balanced or ambiguous or at least non-stupid treatment of good/bad
The saga of A Song of Ice and Fire has sold around 7 million copies (Wikipedia) and it's extremely far away from Manichean morality. I would estimate that no more than five percent of the text involves truly heroic or truly depraved characters.
Sven Hassel's best-selling books can also be a good example. We must, however, distinguish between works that derive their nuanced morality from an attempt to be faithful to reality, and those that donate nuanced morality to a fictional setting.
If we go back in time, we find emphasis on heroism more than good vs. evil. E.g., the Iliad.
Update: This post has also been superseded - new comments belong in the latest thread.
The second thread has now also exceeded 500 comments, so after 42 chapters of MoR it's time for a new thread.
From the first thread: