The case he makes seems persuasive to me. I think you could make a pretty case for Lyndon Johnson, Richard Nixon or George W. Bush as well.
FDR: Social Security, greatly reduced poverty among elderly citizens, won WW II that if lost would have untold negative consequences, and helped establish a framework of internationalism that avoided another world war, and secured post war prosperity.
Truman: Helped win the war established containment of the Soviet Union.
Eisenhower: Continued to successfully prosecute the cold war, and created the interstate highway program.
Kennedy: As noted in the link stumbled from one disaster to another and began our involment in Vietnam.
LBJ: A good contender for the worst. He started the inflation that was part of stagflation in the 1970’s, but he also passed the civil rights act of 1964. That likely keeps him out of contention.
Nixon: Only President to resign would likely put him in contention, along with dragging on Vietnam. The opening with China is a big deal, but it might have happened anyway. He also began the stagflation of the 70’s He’s in contention.
Ford: I think his pardoning Nixon did the country a big favor, and likely cost him re-election. He’s not in contention for the worst at all.
Carter: I think he deserves a lot of credit for the camp david peace accords that has prevented another Israel-Egypt war. He’s not in contention.
Reagan: Contributed to an economic climate that broke the back of stagflation and won the cold war. A good to great President.
Bush I: Helped balance the budget. Won the first Golf War and kept it goals clear and achievable, unlike his son.
Clinton: Didn’t muck anything up big time and allowed good times. Not great, not awful.
Bush II: Was faced with unprecedented challenges. If he’d kept his focus on a quick victory in Afghanistan and had declared war in Iraq with insufficient thought and evidence he might have been a borderline good President. But with an un-needed war, that was amazingly mismanaged, ending his term with a massive recession, nominating and then withdrawing an obviously unqualified candidate to the Supreme Court, I think he comes off as just not up to the job.
Obama: Not a radical as his many critics insist. However, he does seem disengaged much of the time. He hasn’t come up with a formula to recover from the Bush recession. If health care reform is modified and used to come up an improved system over the status quo in more availability, but lower cost, that would be a great achievement. Whether THAT happens remains to be seen.