Ken Burns struck right tone in an interview done prior to his World War II documentary. Burns explained (to a largely anti-Bush academic audience) that it takes decades for history to properly digest the consequences of a major figure. I recall Burns mentioning thirty years as an adequate time period.
It's been pointed out that Harry Truman was practically chased from office for his management of the Korean War, communism, and the ouster of Douglas MacArthur. MacArthur did not take his dismissal lightly and flaunted his past heroism to the country, further damaging Truman's standing with the American public. In hindsight, MacArthur's arrogance caused the negative turnaround to the UN forces on the peninsula. His recklessness threatened to push the United States into an even deeper confrontation with China. Truman's actions were seen as week in the 1950s; the social upheaval and the Vietnam War put him in better light in the 1970s. Truman's containment policy remained the standard for US presidencies up to George Bush the elder.
I don't see George W. Bush as ever becoming a "good" president in history's eyes. I have never been hateful to the former president during his time in office. In defense of one reason why held support among a segment of rational-minded was the perception him as being decisive. This was not seen a trait of his predecessor. The invasion of Iraq could have been a geopolitical coup against the authority of an inept United Nations; instead, it turned into an expensive fiasco (initially) simply because there was an inefficient occupational policy. The ineptitude became attached the United States and empowered enemy nations in the view that the country's status was in decline.
The handling of energy policy, the detention of prisoners with no plan in sight, his inability foresee the inevitable credit crisis, the defeat over social security reform, and the failure to reform the immigration system all show a presidency with policies that weren't thought-out.