I'm not sure whether you're asking for two different movies or one. I wouldn't really consider my favorite movie the best movie of all time. I would reserve that for a film that really did something special for films overall and is historically important. Maybe something like Citizen Kane, Casablanca, Dr. Strangelove, Annie Hall, Raging Bull, etc. Overall, Citizen Kane is considered by most to be the greatest film of all time.
My favorite movie is Ghostbusters.