I think this is an important question to ask if we want to get an honest perspective of the real human toll of the Iraq war.
I just came across the following article by Amy Hess in the usconservative, which argues that a US soldier aged 18-35 is only slightly less than twice as likely to die at war than an average american of the same age.
But the methodology used is seriously flawed: She compared the ratio of deaths in Iraq to total troops in Iraq to the ratio of deaths in America to citizens in America. She estimated that about 1.5 million troops had served in Iraq over a 3 year period.
This estimate is fine, but using the total number of troops who served over 3 years ignores the fact that each of those troops only spent a fraction of that time in Iraq.
To be exact, the average length of a soldier's deployment is 300 days. So Amy Hess is comparing the death rate of Americans over a 3 year period in the US to the death rate of troops in Iraq over a 300 day service period. This should throw her estimate off by a factor of 3*365/300=3.65. Factoring this is, we get an estimate that American soldiers in Iraq are about 2*3.65=7.2 times more likely to die than their compatriots at home.
There are certainly some flaws in this estimate too (such as the issue of multiple deployments), but I think it's a good deal more accurate than what this author has done.