Harry Potter and the Philosopher's Stone

Essential, and start here rather than with Fantastic Beasts, whatever the chronological toggle offers. The prequels are written for people who already know what Dumbledore and Grindelwald are to each other, and this is the film that has to build a world from nothing.

Chris Columbus was hired to be faithful and he was, to a fault. Very little is cut, scenes play close to the page, and the film's job is essentially architectural: this is what a wand shop looks like, this is what the Great Hall looks like, this is a staircase that moves. Everything the next seven films take for granted is established here, which is why it is the slowest of the eight and why it had to be.

The casting is what endures. Not the children, who are eleven and are visibly eleven, but the adults: Alan Rickman playing a part whose entire point would not be revealed for a decade and playing it correctly from the first scene, Maggie Smith, Robbie Coltrane, and Richard Harris as a Dumbledore considerably frailer and stranger than the one who replaced him.

It is a children's film in a way that the series stops being around the third entry, and that is worth knowing rather than holding against it. The chess game and the troll are the set pieces, the photography is warm and flat, and John Williams wrote the theme that every subsequent composer had to work around.