The Gipper was a nickname of the person Reagan played in a movie. People attached it to Reagan in reference to that performance.
The Donald is a marketing creation of Trump himself, putting his ego on full display.
One is a compliment, one is marketing being lapped up.
No.
People widely didn’t call him that just because they liked some old movie he was in. It may have started like that for a very small group, but it became part of the “marketing” for Reagan no different than “the Donald” is for Trump.
Both are nicknames that people use. There isnt anything positive nor negative about it. Certainly nothing having to do with deifying him.