The job of being President is a glorious one, but also one of heavy burdens and responsibilities, and being popular when President and throughout your lifetime is a rare occasion.
So when one looks at 20th and 21st Century Presidents, only a few remained widely popular, even in the midst of crisis, and also in the years after retirement.
The only Presidents to have widespread popularity while in office and in retirement are:
Theodore Roosevelt
Dwight D. Eisenhower
Ronald Reagan
Bill Clinton
Interestingly, all of the above are Republicans, except for Democrat Bill Clinton, who has just been judged the most popular President in the past 25 years!
All of these Presidents above, with the possible exception of Eisenhower, possessed great charisma, and while Eisenhower was not a great public speaker, his military heroism and leadership in World War II made him much honored, loved, and respected, for the rest of his life!