In discussions, I'm often confronted with the view that the holocaust "could have happened anywhere" with comparisons drawn to Armenia, Rwanda, etc. Somehow this doesn't sit well with me. Is it appropriate to consider the holocaust as "just another genocide" historically? Is there a historical debate on the "uniqueness" of the holocaust, or do historians contextualize it terms of other genocides?
There is an immense body of literature on this topic, stemming from the Historikerstreit of the late '80s. As is often the case, there's no "correct" answer to this question. However, if you're looking for historians and arguments to counter the "it could have happened anywhere" or "Stalin was just as bad" lines of reasoning, you should take a close look at Hans-Ulrich Wehler and Hans Mommsen as starting points, both legendary historians in their own right. Much of the original material appeared in newspapers and journals, but Reworking the Past (Baldwin, ed.) is a slightly dated, yet still useful text as well.
Could you explain a little about what you mean by "unique"? The Holocaust was more centrally-planned than many of those other genocides, and also in a country that the Western world considered unusually cultured, and those features make it particularly compelling and scary for some people. But whether those features make it unique in a different way than the way in which those other genocides are different from one another is really a question about how you categorize genocides, not about anything that happened or about the people who were killed.