Per the conventional wisdom, there's little doubt -- thinking of Bush administration from beginning to end, it's an eight-year stack of epic fails which, taken together, comprise perhaps the ultimate, the Great Pyramid, of Fail. Here's the criterion:
I do solemnly swear (or affirm) that I will faithfully execute the office of President of the United States, and will to the best of my ability, preserve, protect, and defend the Constitution of the United States.
Fail, fail, fail from the original theft of the position in 2000 to the economic collapse of 2008, with two lost wars abroad and one fairly successful war -- on our civil liberties -- at home in between.
But ... "failure" presupposes an objective which has not been achieved, and it's by no means obvious that George W. Bush's objectives were those contemplated in the Constitution.
We know Bush's history, and it's a history of getting the things he wants through politics, often welshing on any repayment due.
He wanted to avoid Vietnam, and his daddy's politician friends obliged him by securing an Air National Guard billet for him (from which he subsequently deserted).
He bought into a failing baseball team and voila, Austin bailed it out and made it profitable for him with taxpayer money.
He decided he wanted to be governor of Texas, and the voters obliged. They even gave him a second term and he deserted them, too, because he decided he'd rather be president instead.
Is it really any surprise that after stealing the 2000 election (once again with the help of politicians of similar ... character), Georgie would spend the subsequent eight years doing the things Georgie wanted to do instead of the things the job required him to do? And can he really be classified as a "failure" if he got exactly what he intended to get out of his presidency?
IMO, the Bush presidency should be viewed as a (thus far) successful crime spree, not as a failed attempt at "public service." He's lined the pockets of his friends and campaign contributors well, even to the extent of trillions of dollars in new government debt. When he leaves office, he -- and they -- will continue to profit on the speech circuit, on the memoir-publishing gravy train, through gratuitous corporate board appointments, etc.
If Bush is a "failure," he's laughing all the way to the "failure" bank. Matter of fact, I'd suggest that he title his presidential memoir The Joy of Failure: How to Fail Your Way to the Top ... but someone else beat him to the title.