The real Bush legacy (not the one he imagines) can be summed up in one word: Squandered.
At the beginning of Bush's first term, the United States had a balanced budget, moderate debt, healthy and well-equipped armed forces, and a dominant leadership position in the world community. And, after the 9/11 attacks, there was unity within the United States and sympathy from abroad.
What did Bush do with all those assets? He squandered them.
Bush's tax cuts for the wealthy has driven up our national debt to record levels.
The invasion of Iraq and the resulting pressure on our armed forces (while also trying to fight a ground war in Afghanistan) has stretched our military to the breaking point and has depleted so much equipment and morale that it would take years to recover even if the war ended tomorrow.
Our continuing use of violence and threats of violence as a solution to all problems, both on an individual level (Guantanamo Bay, secret prisons, "extraordinary rendition," and the use of what the world considers torture) and a national level (Bush now talks openly of using military power against Iran) has completely negated whatever international goodwill that existed after 9/11, and has undermined our role as a moral and diplomatic world leader.
And, the unity that arose after 9/11 was effectively killed by the realization that we'd been manipulated at best (lied to at worst) in Bush's rush to invade Iraq.
Now we're facing real threats, both in a looming recession and continuing fall in the value of the dollar, and in the rise of the power of the Taliban in Afghanistan and Pakistan, and we've got nothing to fall back on. Bush squandered the economic and military resources we should have kept for emergencies.