Reagan was far more popular after leaving office than he was before. Kind of “you don’t know what you got til it’s gone”. People realized what a great President Reagan was. When he was in office I remember jokes about him being a B actor or laughter about commercials he did.
Trump had 10s of thousands chanting “we love you” to Trump at rallies. So yes President Trump is indeed more populat than any President.
There was all that talk about how Reagan might be getting a little dotty in his dotage, which unfortunately turned out to have perhaps been true. I was not a fan when he went in but at the end I remember choking up thinking the old Irishman did it, he turned everything around. And things more or less stayed turned around till well, until 2008 really, and 2009. Despite everything BJ and the Beeyotch tried to do to it.