First, we did rid the world of Saddam. That is no small thing. He was a menace. We forget now just how much of one he was, but he was a menace indeed. He could have done great damage had he stayed in power.
Second, he still did have traces of weapons of mass murder (WMM — a better term than WMD). And he had maintained the capability to rapidly rebuild his stocks. The sanctions regime, undermined by a massive oil-for-food scandal, was eroding. Europe was, as is its wont, being Europe, meaning feckless and corrupt. Saddam was about to outlast its will. Furthermore, there is some reason to believe he had even more WMMs, and that he spirited them to Syria, as Israeli intelligence suggested at the time. If that is so, then the whole WMM subject takes on a different light, one that makes the military eviction of Saddam look far better.
Third, the Iraqi people welcomed representative government with enthusiasm and courage. Their first and second post-Saddam elections — the voting process, not the results — were inspirational. And they catalyzed a series of similar movements elsewhere — the Orange Revolution, the Rose Revolution, the Cedar Revolution, etc. — which provided hope to millions. Granted, the Bush administration’s mishandling of the military situation and the reconstruction — until it finally tried the surge in 2007 – threw away most of the benefits. But then the troop surge worked, and Iraq stabilized, and it became for a while a useful ally in the region.