The Washington Post has a series about how Bush will be remembered:

• He’s The Worst Ever 
  …somehow, in his first six years in office he has managed to combine the lapses of leadership, misguided policies and abuse of power of his failed predecessors. I think there is no alternative but to rank him as the worst president in U.S. history.
• Move Over, Hoover
  Bush has two more years to leave his mark, he argued. What if there is a news flash that U.S. Special Forces have killed Osama bin Laden or that North Korea has renounced its nuclear program? What if a decade from now Iraq is a democracy and a statue of Bush is erected on Firdaus Square where that famously toppled one of Saddam Hussein once stood?
  …truth is, after six years in power and barring a couple of miracles, it’s safe to bet that Bush will be forever handcuffed to the bottom rungs of the presidential ladder. The reason: Iraq.
  …
  His presidential library will someday be built around two accomplishments: that after 9/11, the U.S. homeland wasn’t again attacked by terrorists (knock on wood) and that he won two presidential elections, allowing him to appoint conservatives to key judicial posts. I also believe that he is an honest man and that his administration has been largely void of widespread corruption. This will help him from being portrayed as a true villain.
• Time’s on His Side
  … Perhaps Bush can take solace in the case of Harry S. Truman, who was reviled at the end of his presidency, with approval numbers hovering around 30 percent. Too liberal for conservatives and too conservative for liberals, Truman was saddled with an unpopular stalemate in the Korean War and accusations of corruption at home. Many saw him as a belligerent rube, too unsophisticated for the White House.

  Today, however, many historians have revised their estimate of his presidency upward. There certainly are echoes of Truman in the current carping about Bush.
  …
  No one expects historians to be perfectly objective. But history should at least teach us humility. Time will cool today’s political passions. As years pass, more documents will be released, more insights gleaned and the broader picture of this era will be painted. Only then will we begin to see how George W. Bush fares in the pantheon of U.S. presidents.

• At Least he’s not Nixon
  Bush has two years left in his presidency and we don’t know what they’ll hold. They may be as dismal as the first six. Future investigations may bear out many people’s worst fears about this administration’s violations of civil liberties. And it’s conceivable that the consequences of the invasion of Iraq may prove more destructive than those of Nixon’s stubborn continuation of the Vietnam War. Should those things happen, Bush will be able to lay a claim to the mantle of U.S. history’s worst president. For now, though, I’m sticking with Dick.