I'll start by answering the part of your questions about other atrocities. I believe it's as simple as: the Holocaust happened in Europe, which is where most of the developed world was looking at the time. Also, the West had managed to convince itself that it had outgrown atrocities, only to see them appear in its courtyard.

Now, as to why we are still talking about it, I believe it's a pretty good thing.

This does not mean that we should not also talk about other atrocities. Definitely, they should be taught and discussed and shown.