You paint a really nice, neat scenario which might possibly exonerate Bush on Iraq. You're right, from a historical point of view the jury is still out because Iraq has yet to work itself out.
40 years from now it might come out more that his administration manipulated and misinterpreted faulty evidence more than what's been proven as fact now. 40 years from now we now may look back at a middle east no better, more violent after having been hit by terrorists several times because of his error in judgement. We don't know.
From where I'm sitting based on what we do know about the history of long, costly occupations and nation-building, not to mention what's happened on the ground in the past few weeks--Iraq doesn't look good. A democratic Iraq is supposed to be the cure-all tonic to pave the way for peace in the middle east. We'll have to see where we are 40 years from now. We do know that hatred of the west emerged out of Imperialistic designs of Europe in the region in the early 20th century. Yet the United States is military occupying a Muslim country in the middle east. Definition of insanity? I think so.
I also think we can fall into this trap of "we don't know anything about a presidency, so we shouldn't criticize" because of the lack of a historical record. I think these exercises have their limitations, like all counterfactual history.