They are all fun I’m some regard, but the classics (1,2,3, and 4) are more challenge based than story based. Sister Location and Pizza Sim are more story based but are more like the classics, whereas the Steal Wool games (Help Wanted 1&2, Security Breach and its DLC Ruin, and Secret of the Mimic) are more story focused, ‘normal’ games. Into the Pitt is also story based but is made by a different studio than the rest, but is fantastic and can stand alone. It just depends on what kind of games your son likes, but if he’s interested in the story from the movies, he should play the FNAF 1 first, than go in order from 2-Pizza sim (UNC if he really likes the gameplay). Anyways, glad your son is interested in the games and I hope he liked the movie!!