There's an interesting article here by the German historian Götz Aly. Starting from a commendation of Raul Hilberg's monumental The Destruction of the European Jews - a 'book [embodying] the work of a man who has spent his entire life trying to see something that many of his contemporaries did not see and did not want to see', and 'breath[ing] the unbroken search for truth by its author' - Aly argues that the empirical work is now available that will enable a proper placing of the Holocaust in its comparative historical context. The earlier would-be contextualization by Ernst Nolte and others during the Historikerstreit was a plain effort at apologetics. But the same need not be true of a comparative exercise today:
A historiography that takes such facts ['of ethnic segregation, expropriation and extermination'] into account should not relativize the Holocaust and the central responsibility of the Germans; distinctions must be made between specific cases... Nonetheless, a historiography that takes itself seriously must recognize the patterns and pick up the threads of Europe's history of violence and progress in the first third of the twentieth century in order to localize Auschwitz in historical terms.Comparison is unavoidable, even to establish singularities. It doesn't have to be a vehicle for apologia.