My favorite fan theory regarding how Fury Road's Max isn't like Gibson's, and only the very old seem to remember pre-apocalypse times: this "Max" is the Feral Kid from The Road Warrior, having grown up and assumed the persona of Mad Max.
I like it.
And besides, isn't there a scene in this film - I haven't seen it yet - where Max has a vision of his family, and the child is a girl? In the original, Max and his wife only had a son (Sprog).
Though Hardy's Max wears a knee brace like Mel Max from TRW - which he had to wear after being shot in the knee in the first film.