For now I'll name Obama as the worst president. Carter was out of his depth but Obama was actively trying to undermine his government and country.
So, who's the worst of this bunch? The finalists are Clinton and Obama. Both left the country worse off than when they took office. Carter was at a loss on how to handle the sky-high inflation. Obama never figured out why the economy was growing less than 2% when it should have been growing more than 3%. Carter was at a loss to stop the spread of communism in South America. Under Obama, we saw more than half of the youth decide that communism is better than capitalism.
On to Obama. He took office during the worst downturn since Reagan, possibly since FDR. While he didn't mess up the recovery, he didn't help it, either. We had the slowest post recession growth since FDR, probably for the same reasons - expanding government. The stimulus package didn't stimulate. Obamacare was unpopular and had to be propped up by (unconstitutional) executive orders. Obama was handed a stable Iraq and managed to mess it up by pulling all of our troops out and not taking ISIS seriously. Obama was determined to sign a treaty with Iran and allowed the Syrian civil war to grow into a humanitarian crisis rather than offend Iran. He mocked Romney for calling Russia our most important geopolitical rival. He called his Korean policy "strategic patients" but it really amounted to kicking the can down the road. He was part of the overthrow or Libya and allowed it to sink into a failed state humanitarian crisis. The rule of law saw severe hits as his administration expanded executive and administrative reach. After saying dozens of times that he didn't have the power to allow "dreamers" to stay, he did it anyway. Title IX was similarly stretched to the breaking point. The public had been polarizing for years but this accelerated under Obama. We have the most turbulent times since the 1960s but no war and no civil rights movement to explain it. People are just polarized and angry and the Obama administration fed this. The IRS was weaponized under Obama, delaying applications for groups they disapproved of for years while approving favorable groups in a few weeks. The Justice Department may well have been politicized, too, as information is leaked out about the handling of confidential messages on Hillary Clinton's private email server.
Bush 43 is another mixed bag. The economy did fairly well under him and he was far more moderate than he's given credit for being. 9/11 was not his fault but his response to it was questionable. There's no question that we needed to overthrow Afghanistan in order to break up al Qaeda. Similarly, we'd never actually ended hostilities with Iraq before Bush toppled the country. In both cases, his administration discovered that it's far easier to overthrow a government than it is to set up a stable replacement. If he'd taken the route that Obama did in Libya and left the two countries alone then both would probably be failed states and humanitarian disasters but Bush would be held in higher esteem. Similarly, if Bush had had a 3rd term then he might have managed to clean up his messes. He managed to turn Iraq around and stabilize it by the end of his presidency. While Obama takes credit for saving the economy, the crisis actually came during Bush's last months and he stabilized it before leaving office.
We saw mild but steady growth under Clinton punctuated by the tech bubble. Near the end of his term, Clinton rated himself as a solid B president and was hoping to raise his score with a diplomatic victory like the Camp David Accords. This eluded him so he remains a B.
It's not unusual for a sitting vice president to run and finish in a close race. Bush won in a landslide. He was a competent president but seemed out of touch and a minor recession was enough for him to lose reelection.
I've already ranked Reagan as best, so skipping on to Bush 41...
Ford replaced Nixon and Carter replaced Ford, coming in with overwhelming approval ratings. He was not up to the job. Inflation soared, unemployment remained too high and eventually the economy crashed hard. He continued Ford's "detente" with the USSR which led to Soviet expansion. The friendly Shaw of Iran was overthrown and Carter helped place a constitutionally elected government in place only to see it overthrown and a theocracy set up in its place which is still a problem. After that, "students" with the support of the government overran the American embassy and took the staff hostage for months. The only good thing to come out of the Carter administration was the Camp David Accords which Carter facilitated between Israel and Egypt.
Nixon's a very special case. He continued LBJ's expansion of government with such things as the National Endowment for the Arts and for the Humanities. He expanded Viet Nam before getting us out. He opened relations with China. He was reelected in a landslide, winning 49 states. But he managed to get himself impeached and he always was hated by a significant portion of the population. He also oversaw the beginnings of the economic problems that dominated the 1970s.
LBJ's administration is even more mixed. Where JFK dipped his toe into Viet Nam, LBJ jumped in with both feet. He gave us Medicare and Medicaid and expanded Social Security. All of those programs are popular but none of them are sustainable in the long-term. The most important civil rights advances came during his administration and he was more supportive of them than he is given credit for.
Eisenhower was competent. JFK is a mixed bag. He gave us the space program. He didn't advance civil rights as far as he could have and he got us into Viet Nam, although in a limited way.
So, onto the worst.
First off, the best president is Reagan. There were problems during his administration, mainly Iran/Contra, where he openly defied Congress. There were some other mistakes but he changed the course of politics. It shows how influential he was that Barack Obama was openly musing about being a similarly transformative president in 2008. When Reagan came to office in 1981 the country was a mess. We were in the worst economic downturn since the Great Depression (in some ways it was worse than the Great Recession). The Soviet Union was expanding and the military contracting. People didn't feel very good about America. Reagan kicked off the longest peacetime economic expansion in history, put in place policies that ended the Soviet Union and left America feeling good about itself again.
It's President's Day which originally was Washington's Birthday but then they combined Washington's and Lincoln's birthdays into a single holiday and moved it to Monday. Anyway, it's an excuse to name the best and worst presidents of my lifetime. I'm only including them because I don't have personal experience with any others and it still covers a 60+ year spread.I'm not going to include Trump. He's only 13 months into his presidency. I'm going to skip Ford for the same reason. He wasn't in long and didn't have much impact. I'm including JFK because he completed most of his term and did have an impact.