Possible factors for the primacy accorded the Holocaust vis-a-vis other terrible historical happenings:
1. Many exiles and survivors immigrated to English-speaking countries and their accounts are widely available. Not so Bosnians, Hutus, etc.
2. Remembering how terrible the Holocaust was is part of a natural tendency to justify the enormous cost the Allies paid to see the war through to unconditional surrender.
3. It is a fact that a disproportionate amount of the heads of Hollywood studios, who mostly shape how we view history these days, have been Jewish. While not a reason by itself, it can't hurt.
4. The Nazis are the one enemy everyone can agree on loathing. Virtually nobody defends them, unlike every subsequent regime accused of crimes against humanity. See, for example, Ed Herman's (Noam Chomsky's co-author on Manufacturing Consent) denial of the 1995 Srebernica massacre.
5. The Nazi crimes are generally better-remembered as a result of guilt on the part of influential leftists in the press and academy who were initially forced by Stalin to defend the Molotov/Ribbentrop Pact. Making up for lost time.
6. As already discussed, for good or ill the Western mind is more affected by the country of Bach and Goethe sending millions of people to gas chambers via railroad than what happens in Cambodia or Rwanda, however terrible it is.
