The war in Syria has been brutal:
As bad as the war in Iraq was (after Saddam was overthrown), it been much worse in Syria. In Iraq the worst year was 2007 when nearly 18,000 died. Next door in Syria the 2015 death toll was 55,000, which was down 38 percent from the 76,000 in 2014. So far 2016 appears to be worse than 2015, in large part because Russia and Turkey are now actively involved and most factions (pro-Assad and pro-rebel) are at war with ISIL because ISIL has always demanded that everyone submit to their rule, including other Islamic terrorist groups.
Not that we didn't have a tough fight in Iraq. But we did manage to crush a series of conventional, insurgent, and terrorist threats (and that post doesn't include the Awakening/Surge that finally broke Sunni Arab resistance and the campaign against pro-Iran Shia death squads that broke their power by the spring) by spring 2008. That was just 5 years to mostly wiping out the resistance to a democratically run post-Saddam government.
Sadly we took our foot off their necks by 2011, and we're back in Iraq War 2.0.
Which still doesn't match Syria in the body count metric.