We seem to be selective about what genocides we remember and which ones we don't. Of course, our various means of socialization in our society has much to do with that. One really has to be interested and aware to find information on his own. The Nazi holacaust was so enormous, it's hard for anyone to be selective about it. Even though, there are holocaust deniers who spend their entire lives researching and writing books and articles trying to disprove it ( i.e. check out the websites for the Barnes Review and Institute for Historical Review). Sometimes genocide happens on both sides as in the Balkans today and, it should be remembered that the Kurds assisted the Turks in the Armenian genocide.
Also, should the Soviet famine of the 1930s be designated as a "Ukrainian genocide", how about the native peoples of the Western Hemisphere, the Congo under king Leopold? Anyway, we definitely have our work cut out for us in preventing this kind of stuff from continuing.