Some of the major issues at stake (BBC Online http://news.bbc.co.uk/2/hi/6045182.stm):
1. The number of Armenians killed: Armenians say that 1.5 million had perished in the sands of Syria while the Turks say that only 300,000 died between 1915-1923.
2. Were the killings systematic? Many governments, historians and the Armenians believe that the massacres were part of an organized plot done by the Turkish government during WW1, however, Turkey contends that many Muslims died in the "turmoil of war" as well.
3. The trials after WW1 ended up with one Turkish official hanged and another thrown in jail, but the big 3 Young Turks tried "in absentia" - not present -since they had run away to Germany.
At least 20 countries around the world since this time period have passed resolutions to express sorrow and sympathy (Argentina, Belgium, Canada, France, Italy, Russia and Uruguay), held prayer days and have officially recognized the Armenian genocide, yet America hasn't. In 1984, the U.S. House of Representatives passed a resolution that called for the President to recognize a National Day of Remembrance of Man's Inhumanity to Man with specific reference to the Armenian genocide. The day was April 24th, the day that the Turkish gov't. arrested 50 Armenian intellectuals and leaders who were then later executed - a day that the Armenians recognize as the offical start of the Armenian genocide.
In recent years, Turkey has denied the U.S. any use of its bases for the invasion of Iraq in 2003. Also, Turkey has urged the U.S. gov't. to block a Congressional vote in 2007 that would recognize the Armenian genocide, and so the House Foreign Relations Committee stalled the bill.
Copy of the genocide map from the Armenian National Institute: http://www.armenian-genocide.org/map-full.html