This is indeed a very important question, especially when it comes to matters of portraying events within and during the reign of the third reich.
The no holds barred, true to life, realistic storytelling is rare in cinema when it comes to this subject.
I can only think of a handful of intelligent, correctly weighted, realistic films that didn't fall into the easy trap of safe, two-dimensional, dumbed down, good vs evil story telling.
As has been mentioned, there were many attempts on Hitler's life, and there were many men and women who had complex emotions and loyalties towards their families, their country and the war, as well as the Nazi party.
There are a wealth of amazing stories that could be told that are not, it's either American propaganda re: d-day, or events in the pacific, then the holocaust, or character drama's about Germans who heroically defied their govt.
What about the story of Poland? or of Rohm and the SA (night of the long knives?), what about operation barbarossa? What of the stories of the European axis powers, such as those who fought and perished in Russia? What about the complex story of the numerous Europeans, from Ukraine to Iraq to France and Norway who fought for the Reich?
In fact it has been left up to the Germans themselves (perhaps with the exception of 'Schindler's List' and 'saving Private Ryan') To make authentic, challenging films about the war.
What comes to mind is 'Das Boot', 'Stalingrad' and 'Unsere mutter unsere Vatter'.
There are a great deal of excellent documentaries covering all theaters, units and battles. The two best would have to be 'The World at War' and the 'Battlefield' series. I personally would love to see a film covering the opening of Barbarossa, the battle of Prokhorovka (Part of the Battle for Kursk) and many more.
It would just take some guts on the part of the film-maker(s) not to pander and fall victim to safe storytelling by making sure to pay homage to the victims of the holocaust unless necessary and to portray the German character's in depth.