As POTUS it was W's job to protect US citizens. He failed on 9/11 and put the World on the path it shakily treads today. The image of Bush sitting in that grade school classroom on 9/11 represents the kind of President he was. A diffident nervous moron sitting around waiting for someone to come and tell him what to do.
Not only did he create havoc. He also made the us debt 10 trillion dollar more. The only reason 9/11 happened was because George W. Bush bombed a bunch of countries randomly. He also lied many times to America and didn't care about anyone else. And don't act like the America was innocent.
While Bush did get us into Iraq and responded badly to Katrina, as well as add 2 trillion to the debt, had an administration that treated veterans poorly and had terrible tactics, he still was rather good.
In his defense, Congress and the Senate voted overwhelmingly for the Iraq war (and there were a few chemical weapons in Iraq), while many organizations believed Iraq had those weapons. Plus, the mayor of New Orleans was told to evacuate but he refused.
However, he did a number of good things. He cut taxes, boosted fetal rights with the Mexico City policy's reinstatement, Partial-Birth Abortion Ban Act, and Unborn Victims of Violence Act. He changed children's education for the better (more or less), had a good response to 9/11, and invaded Afghanistan, signed multiple free trade agreements, lowered violence in Iraq with the 2007 troop surge, and even softened the blow of the 2008 Recession. Finally, he also did a lot for Africa's schools and saved millions of lives from AIDs with PEPFAR.
G.W. Bush was neither the worst or the best US president. It's hard to say what determines if a president is good or bad. Ultimately only time will tell how someone is remembered. In the midst of his presidency Bush was loved by some and hated by some, as is every president. Only after time has passed can you remove emotion from the equation and truly see the outcomes of his policies.