The Holocaust and other catastrophic events have been discussed regularly.
I'd venture to say Turkey is the reason you don't hear to much about the Armenian situation. If memory serves me well, Obama painfully avoided raising the issue for fear of upsetting relations with Turkey. Now you have Trump in office who has publicly praised Turkey's dictator, so the Armenian genocide won't be mentioned anytime soon. Not to mention I can't think of any Armenian organizations with enough clout to press the issue. When I think Armenian, System of a Down and Armenian Power in Los Angeles comes to mind.
As far as Rwanda goes, it really goes without saying why that isn't discussed to much. I'm surprised a movie was made on the subject.