Not trying to be disrespectful. Any tragedy where people lose their lives is bad however I do wonder. 9/11 involved 3,000 people losing their lives. I think way more have been lost during WWII.
In 1994 years before the Rwandan genocide, almost 1,000,000 died within three months in a slaughter.
There are many tragedies which have taken countless more lives yet if you mention anything today, the 'freshest' tragedy is 9/11.
Does it have to do not so much with the death toll but method of attacK? The September 11th attacks were the ultimate deception, using seemingly innocuous commercial transport as weapons of terror. This was unprecedented compared to the other methods of attacks.