Armenian Genocide! Was it a genocide?

The Armenian Genocide just recently within the past decade has been declared a genocide by only 15 countries. Why are some countries denying it was a genocide and really only an ethnic cleansing of their country. Many compare this genocide to the Jewish halocaust because of the similar time period and the way mass murder was happening. Why is it that more emphasis was put on the Halocaust rather then the Armenian Genocide? Why is the the history of the Jewish Halocaust being taught in schools and the Armenian isnt?