In reality, in World War II, there were no “good guys” or “bad guys”. There were belligerent countries that were fighting the war to achieve certain objectives. Some of these objectives are generally viewed as “noble” and “legitimate”, others as “ignoble” and “illegitimate”.
Nazi Germany fought the war to save itself and the whole European civilization from being invaded, conquered and ultimately destroyed by the Bolshevist Soviet Union. Which was, obviously, a highly noble objective.
Since 1944, it was fighting a war (both on Western and Eastern fronts) to save the unique Nazi civilization from being destroyed by the Allied Powers. Given the fact that this civilization made practically all German citizens (with few exceptions) genuinely happy, this objective could also be classified as noble.
Nazi Germany was fighting the war to get back territories taken away from her by the provisions of the infamous Treaty of Versailles. Given the fact that Germany was robbed of these territories at gunpoint (for all practical purposes), it can be argued that this objective was also noble.
The Third Reich was fighting the war to acquire (via invasion, occupation and annexation) territories necessary and sufficient to obtain enough Lebensraum to make Germany self-sufficient in food and key natural resources. While the fundamental objective of these conquests was understandable (to make sure that the horrors of Blockade of Germany never happen again), this war was more than ignoble – it was outright criminal.
And, finally, being run by national-sociopaths, Nazi Germany was fighting the war to make nations in the East (Poles, Russians, other Slavs, etc.) their servants and even slaves. Obviously, this objective was criminal as well.
Western Allied Powers fought to liberate Western European nations (France, Benelux, Denmark, Norway, Greece) from Nazi occupation. Which, obviously, was a highly noble objective.
They also fought to invade and occupy Greater Germany (Germany & Austria), destroy the Nazi civilization and replace it with the liberal-democratic political, economic and social system. Given the fact that about 90% of German population supported this regime and were genuinely happy in Nazi Germany, this ‘liberation’ was liberation from happiness. Hardly a noble objective.
The Soviet Union was fighting to liberate its territories (as well as Poland, Bohemia & Moravia, Albania and Yugoslavia) from a brutal, oppressive, outright criminal and murderous Nazi occupation. Which was definitely a noble objective.
However, it was fighting to replace German occupation of these territories and countries with only a somewhat ‘lighter’ version of a brutal, oppressive, outright criminal and murderous Soviet occupation. Definitely not a noble objective.
It was fighting to invade and conquer Nazi allies – Bulgaria, Romania, Slovakia and Hungary – to replace political regimes in these countries with a brutal, oppressive, outright criminal and murderous Soviet occupation. An ignoble and an outright criminal objective.