The recipe was the same for the three movies. There was no a real story, gags were numerous and followed on one after another, and the Hui Bros. denounced the HK society shortcomings.
On top of that, each one played very typical characters. With his handsome face and force, Sam was the playboy and the man of action. Ricky always in a daze was usually the scapegoat ending up the laughing stock, but he sometimes could energetically rebel. Ricky was more of a second role compared to his brothers. As for Michael, he portrayed an egoistic and cunning guy whose tactics to get what he wants weren't very honest and sometimes backfired on him.
The marketing was already very sophisticated, since before each film release they launched the movie soundtrack with the theme song generally performed by Sam Hui. The audience knew already the songs by heart before watching the movies. The Hui Brothers were soon considered as the 'fathers of comedy', and Sam the 'father' of Canto-pop mixing western Pop to lyrics inspired of life in HK.
To understand the success of the Hui Brothers first three movies, let's refer to Michael Hui's theory about comedy based on the frequency of gags: "In general, in current comedy people don't laugh a lot. In my movies, I try to have a really funny gag every minute. The story is only there to tie them together."