When you evaluate a presidency still 6 months away from beginning its legacy, it is important to compare it with evaluations of other presidents at the same point in time. 6 months before the end of Lincoln's presidency, about 75% of the country thought he was a madman. He had suspended Habeas Corpus, for you pinheads, that means we had no justice or rule of law, it was probably the only time in American history we were a fascist totalitarian government. Now, in retrospect, we all love Lincoln and praise him as one of our greatest presidents, but such was not the sentiment of the day, in fact, it resulted in his assassination. He literally divided this country against itself and engaged in an all out civil war, something Bush never did, in spite of the liberal treason and attacks on America.
Another president we may consider is Andrew Jackson. While we see him on our $20 bill, and think he was one of our greatest leaders, his policies as president often met with disfavor. He completely oppressed the Native Americans, relegated them to savages and barbarians, and marched them to their deaths along the Trail of Tears because he was prejudiced against them.
There are any number of presidents who, 6-months before the end of their presidency, people viewed as "bad presidents" or "the worst ever" president. In fact, it is precisely where the term "lame duck" came from, people who were disgruntled with the lack of achievement in the last days of an administration.
Bush made his share of mistakes and blunders. The objective and purpose behind Iraq was good, but the planning and implementing was not as good as it should have been, and the administration sorely lacked the communication abilities to combat the anti-war arguments along the way. Like his father, Bush literally ignored public sentiments and failed to address the issues raised at the time, which led to catastrophe. Like his father, he assumed the record high approval numbers he enjoyed would last, and he wouldn't have to do a thing to make that continue. I rank him just below his father as presidents go, and his father is along the same lines as Gerald Ford, nothing much to brag about. The Worst Ever? I don't know about that, history will tell.