Most importantly, there has not been another terrorist attack on the US since 9/11. That should be a cause of celebration - it's difficult to point to the absence of something and say "see what I have done", but in this case it is important. People are still flying, going about their daily business, albeit with much less convenience than they once did.
Bush critics point at failure to achieve peace in Israel, although the ceasefire between Hamas and Israel points to at least one step forward. The isolation of Hamas in Gaza has worked to prevent the entire Palestinian Authority from becoming an Islamist terrorist base. Meanwhile Israel has knocked out a nuclear facility in Syria, something that the so called "anti-nuclear/peace" movement wont ever give credit for. You see to them, it is no worse for a one-party state or Islamist theocracy to hold nuclear weapons, than for a liberal Western democracy to do so. The very same people also claim to support feminism and human rights, when they treat regimes which in practice reject both as being no worse than the USA or the UK.
However I digress. Other criticisms of the Bush administration are around climate change - a reasonable concern, which has become a fad for armageddon like calls for radical intervention in the forms of taxes, subsidies and regulations in Western liberal democracies, whilst rapidly growing developing countries and oil rich states which per capita are as wealthy as Western democracies are expected to do nothing. Meanwhile the rising price of oil, due to demand and tax/regulatory/planning restrictions on supply (of both crude and refined product) have done more to reduce energy use (and in more efficient ways) than any nonsense about subsidising alternatives.
There is criticism on the economy, with some justification, but the current recession is led by the end of a property/credit boom that started well before Bush, as well as oil prices. More could have been done, certainly government spending has ballooned under Bush where it could have been cut back to ease the pressure on credit through the budget deficit.
Where criticism is valid has been in two areas:
1. The erosion of civil liberties as part of the war on terror, whereby wire tapping and interception is now a routinely used power by law enforcement authorities. The ability to use these powers is insufficiently monitored or limited. In short, law enforcement agencies have asked for powers they long dreamt of, because they believed it necessary to fight the war on terror - these requests have sadly not been sufficiently questioned.
2. The use of torture and rendition. In a state of war, it is difficult to determine the line between detaining suspects who are planning and aiding and abetting the waging of war against your country, and when people should be charged and tried for offences in a civilian court. The current situation is a blurring between those. It is important that those who are detained do face trial, and do have the right to defence. The risk of arresting and detaining the innocent is real, as is the risk that being deterred from doing so results in acts of terrorism being undertaken. The balance has been successful in preventing further terrorist acts, but it is important to be seen to be treating suspects fairly and impartially. Of particular concern has been the use of torture to obtain confessions and intelligence. Its efficacy is actually greater than critics make it out to be - those who face severe discomfort and pain are less capable of constructing consistent lies than spilling the truth. However, it's morally repugnant. It is difficult to spread the values of individual rights and liberty when you engage in practices that are milder versions of those you oppose. Fortunately both McCain and Obama reject it.
Some libertarians will see those last two points as self-evident that Bush is no friend of freedom. I disagree. He is a flawed friend of freedom. I have not mentioned his evangelism deliberately, largely because it has been exagerrated by his critics. As an atheist myself, the use of religion in a political context beyond demanding the simple right to freedom of belief appalls me. However, despite the fears of some he hasn't implemented a theocracy in the USA. His use of some theocratic language has been counterproductive, as it feeds the Islamists to talk of crusades, but despite his strong religious beliefs (and don't forget both Al Gore and John Kerry both claimed similar strong faith) it has not significantly undermined the fundamental secular nature of the USA.
Andrew Roberts in the Daily Telegraph believes that history will judge Bush well. It is frankly too early to say for sure, six months is a very long time in politics (New Zealand had three Prime Ministers in that time in 1990). He says:
"The overthrow and execution of a foul tyrant, Saddam Hussein; the liberation of the Afghan people from the Taliban; the smashing of the terrorist networks of al-Qa'eda in that country and elsewhere and, finally, the protection of the American people from any further atrocities on US soil since 9/11, is a legacy of which to be proud.
While of course every individual death is a tragedy to the bereaved families, these great achievements have been won at a cost in human life a fraction the size of any past world-historical struggle of this magnitude.
The number of American troops killed and wounded in Iraq and Afghanistan is equivalent to the losses they endured - for a nation only a little over half the size in the mid-Forties - capturing a single island from the Japanese in the Pacific War."Iraq has not become Vietnam.
So ask yourself this, what would have been different under Al Gore or John Kerry? 9/11 would still have happened, but would Al Gore have overthrown the Taliban? Who knows. Certainly Saddam Hussein would still be in power in Iraq, does anyone really believe he would have just peacefully gone about oppressing his people and not tried again to wage war? Does anyone believe he wouldn't have tried to find common cause with Islamists (as the nominally secular Syria has done) to continue to wage war against Israel, the West and his neighbours to the south? Does anyone believe that Gaddafi would have surrendered?
Do you think there would have been any difference to global warming had Al Gore signed Kyoto? Remembering that Russia, India, China and the Middle East wouldn't have changed behaviour one iota (yes Russia is part of Kyoto but then you can be when your population is in freefall decline). Think that pouring loads of US taxpayers money (money they have spent themselves on other things) into subsidising biofuels more or electric cars would have made any difference at all? You think that a Presidency that sought approval from the likes of China and Russia to act (through the UN Security Council) would have been a deterrence to further attacks like 9/11? You think Hamas would have stopped shelling Israel had Israel been told to compromise more with it?
Of course, "what ifs" can never be proven - but one thing is sure. Since 9/11 there hasn't been another terrorist attack on US soil. Given the scale and seriousness of that one event, that is worth acknowledging. The only ones who wouldn't acknowledge that are those that cheered it on, like Annette Sykes or Barack Obama's former pastor, or those that cobble together fragments to consider it was all a conspiracy.
The USA couldn't organise a successful assassination against Castro, Kim Il Sung, Kim Jong Il, Saddam Hussein, Muammar Gaddafi or Ayatollah Khomeini after all.