Here's a partial list: Saddam is dead. Had he remained in power, we would likely still believe he had WMD. He would have been sitting on an oil bonanza priced at $140 a barrel. He would almost certainly have broken free from an already crumbling sanctions regime. The U.S. would be faced with not one, but two, major adversaries in the Persian Gulf. Iraqis would be living under a regime that, in an average year, was at least as murderous as the sectarian violence that followed its collapse. And the U.S. would have seemed powerless to shape events.
Instead, we now have a government that does not threaten its neighbors, does not sponsor terrorism, and is unlikely to again seek WMD. We have a democratic government, a first for the Arab world, and one that is increasingly capable of defending its people and asserting its interests.