The Baghdad journalist who sent George Bush a "goodbye kiss from the Iraqi people" by flinging shoes at his head probably spoke for many people in the Arab world, where the American leader is widely disliked. The extraordinary incident gave added point to a broader question increasingly asked as he nears the end of his eight-year term in office: was George Bush the worst ever US president?

Any objective answer depends to a considerable degree on how "worst ever" is defined. Opinion polls among American voters, conducted since Bush entered the White House in 2001, are influenced by the fact that people experienced him in real time. They had no similar exposure to, say, slave-owner Thomas Jefferson or civil war general Ulysses Grant.

Undeterred, respondents to a Rasmussen poll in 2007 came down hard on their current leader. As is usual in such contemporary polls, George Washington, Abraham Lincoln and Franklin D Roosevelt were rated among the best ever presidents. Only two were viewed unfavourably by a majority of those surveyed: 60% thought badly of Richard Nixon; 66% thought even worse of Bush.

A Quinnipac university study in 2006 asked voters: "Which of these 11 presidents since 1945 would you consider the worst president – Harry Truman, Dwight Eisenhower, John Kennedy, Lyndon Johnson, Richard Nixon, Gerald Ford, Jimmy Carter, Ronald Reagan, George Bush Sr, Bill Clinton and George W Bush?"

Bush the younger won hands down, with 34% picking him as the worst, followed by Nixon (17%) and Clinton (16%). And these findings are more favourable to Bush than more recent surveys.

Seventy-six per cent of respondents told CNN last month that they viewed Bush unfavourably – the highest negative rating since polls began 60 years ago.

Bush also fares badly in polls of American historians and academics (who are assumed to be more knowledgeable and objective). But these surveys also reveal some tough, albeit obscure, competition for the title of worst ever.

The little-remembered Franklin Pierce, president from 1853 to 1857, is castigated for expanding slavery in the west and thus bringing the civil war closer. Another antebellum president, James Buchanan, is also taken to task for failing to avert the south's secession.

Warren Harding's White House tenure from 1921 to 1923 was marked by notorious scandals and resignations. Under him, it is claimed, the US regressed into a period of isolationism, nativism, and recession, ending with the Wall Street crash. Even more useless than Bush, in an existential sense, were William Henry Harrison and James Garfield, both of whom died after less than six months in office.

But poll numbers are not the only, and not perhaps the best, way of judging presidential performance. Presidents, obviously, can be both both "good" and "bad". Nixon is an example. He is reviled for his Watergate lies. But he is also remembered for ending the Vietnam war, opening up relations with communist China, and seeking detente with the Soviet Union.

And then there are specific measures. If the foremost duty of a president, as US commander-in-chief, is to protect the American people from murderous attack by foreign enemies, then Bush clearly failed momentously on 11 September 2001. He failed to see al-Qaida coming and failed lamentably to stop them. Yet much the same could be said of the otherwise admired Roosevelt, who was caught napping by the Japanese at Pearl Harbour in 1941.

Some maintain the president's main job is to ensure and enhance the nation's economic wellbeing and overall prosperity. The ongoing, made-in-America credit crunch and the global slump that has followed point to Bush as all-time biggest bungler. But that would be to ignore the disastrous contribution of Herbert Hoover, president from 1929 to 1933, and a principal author, by some accounts, of the great depression.

By the time Hoover left office, 25% of Americans were jobless and hundreds of thousands were living in tent cities known as Hoovervilles. Americans couldn't even have a drink to drown their sorrows, thanks to prohibition. Like Bush, Hoover is said to have become depressed. Walking into a room with him in it was said by one contemporary to be like falling into a bottle of black ink.

Bush has failed to win or even finish the wars he started, in Afghanistan, Iraq and the wider "war on terror". But that was true of Johnson and Kennedy. And unlike Iraq, their Vietnam misadventure nearly tore America apart. Even the sainted Abe Lincoln presided over and ruthlessly prosecuted a civil war that killed more Americans (up to 700,000) than any single war before or since.

And if the US president is to be regarded as a figure of moral authority, embodying the nation's values and beliefs, then Bush's personal behaviour has been exemplary compared to many incumbents, and notably that of his immediate predecessor, the intern-challenged Clinton.

All told, it can probably be generally agreed, except by the stubborn rump of conservative Republicans who think him wonderful, that Bush has been a pretty poor president, and possibly the worst in living memory. But when it's recalled what other American leaders have got up to, going back to the founding fathers, circumspection is required.

Those early leaders' treasonable behaviour, their promotion of slavery, their genocide against native Americans, and their later imperial adventures in Mexico, in the Philippines, Cuba, China and beyond set appalling precedents.

Along with everything admirable and honourable that the US and its leaders have achieved, Bush was both heir and product of this tainted legacy. Inescapably, Barack Obama is too.