From 1933 to 1960, America had nearly three decades of fairly successful presidencies — through the Great Depression, World War II, the Cold War, and the threat of nuclear Armageddon.

Franklin Roosevelt, Harry Truman and Dwight Eisenhower were re-elected. While contemporaries were critical of them, they proved successful, stable executives.

In Roman times, the equivalent would have been the period of the "Five Good Emperors." The 18th-century historian Edward Gibbon famously remarked of the reigns of Nerva, Trajan, Hadrian, Antoninus Pius and Marcus Aurelius, between 96 A.D. and 180 A.D., that theirs was a time when "the condition of the human race was most happy and prosperous." This was lost with the succession of the erratic and unstable Emperor Commodus.

In contrast, there has been no such stability during the last 50 years in this country, even as we have become ever more wealthy.

John F. Kennedy was assassinated. Lyndon Johnson was destroyed by Vietnam and did not seek re-election in 1968. An impeached Richard Nixon resigned. Gerald Ford was neither elected nor re-elected. Jimmy Carter was gone after one term — leaving office with a world abroad more dangerous and this country less affluent.

Ronald Reagan sought a renaissance of American order and stability, but by 1986 was caught up in the Iran-Contra scandal. George Bush Sr. was a one-term president who could not galvanize the country.

Bill Clinton was impeached and mired in scandal. The younger George Bush, like Clinton, served two terms but ended his presidency unpopular amid record deficits and incriminations over Iraq.

Now, the once-messianic Obama after six months is already experiencing sinking approval ratings — perhaps because his first budget is $2 trillion in the red.

Is the problem with recent administrations that our presidents do not measure up to a FDR, Truman or Eisenhower? Or have we the voters ourselves become more unstable than our grandfathers? Or is it that the world itself has radically changed what we look for — or need — in our presidents?

By 1960, the United States had become more urban and affluent. Voters began to assume that someone owed us the good life. In contrast, Roosevelt, Truman and Eisenhower had struggled to offer only an equality of opportunity to all: the beginning of civil rights, fair labor laws, overtime pay, disability and unemployment insurance.

But in the next half-century, that limited agenda morphed into one of a promised equality of result.

Then the larger world changed as well. High technology meant that the old radio and print news turned into a 24/7 video stream on the Internet and cable television.

Roosevelt was with his mistress when he fell fatally ill at Warm Springs, Ga. Can you imagine how that would have been covered today? Dwight Eisenhower during the war years had a relationship with his young female chauffeur that today would be blog fare. Truman's old Missouri-machine politics were every bit as dubious as Obama's Chicago pedigree — but largely forgotten when he became president.

Apparently a prior, more gentlemanly media had neither the access nor the technology — nor the desire — to remind us that our presidents were all too human.

In addition, our contemporary commanders-in-chief have had to be "global fixers" as much as American presidents. An AIDS epidemic in Africa would have been beyond Roosevelt's ability to do much about.

But the nature of our leaders themselves has also changed. Recent chief executives certainly seem to have less stature. Harry Truman was outspoken, but Johnson was vulgarly so. Eisenhower wanted to balance the budget, but not in the manner of conservatives like Reagan and the Bushes, who worried less about the resulting spiraling federal deficits. A bald Truman or Eisenhower could not imagine the "cool" of John Kennedy, Bill Clinton or Barack Obama.

Roosevelt fought polio. Truman was once broke and throughout his life remained a common man. Eisenhower led millions of soldiers. In contrast, Johnson and Nixon were known first as political manipulators. The Bushes were born into splendor. Bill Clinton and Barack Obama plugged into the Ivy League and soon after never left the government gravy train.

We have changed. The world is also different. And the types we now elect as our presidents are not like those men of the past. No wonder they seem now more like the mercurial Roman emperor Commodus than the sober Marcus Aurelius — the last of an era.