If I had to choose, I'd say The Labyrinth was more of a childhood favourite, for its delightful range of kooky characters, excellent soundtrack and taboo romantic subtext. But for the sheer existential terror I feel on an almost daily basis, The Neverending Story is probably the film that has had the most influence on me.
I questioned if this would fit the bill - a family film. My instinct is that The Neverending Story was too dark for adults; surely only kids really understood it, right in that deep, dark nightmare place that you lose (somewhat) as you get older.
Bullied young Bastian seeks refuge from his daily torment in a tucked-away corner with a book he stole from a mysterious bookshop. He begins to read about Atreyu, a young warrior who volunteers to venture forth and kill The Nothing - an invisible force that is destroying Fantasia, a world literally constructed from the fantasies of children.
You can take it as metaphor for the slow, unstoppable march towards death but I prefer to think of it as an allegory for the crushing inevitability of adulthood.
When Atreyu's loyal horse Artax is literally consumed by sadness in the swamp (didn't we all have an adolescent Goth phase?) Atreyu and Bastian both finally realise The Nothing ain't mucking around and they're no longer protected by the hubris of youth.
Atreyu rolls up his sleeves and battles through a number of pointless and often violent trials and tribulations. By the time he faces The Nothing, the dude has definitely gone a bit dead behind the eyes.
In the end, the fate of Fantasia rests on Bastian's thin shoulders. He discovers he can no longer be a passive observer but must find the courage to ... yell out a window.
Whatever, the real message of the movie is that if you keep your childhood dreams and fantasies alive, you will never lose the innocence of youth - and that if you wish hard enough you can fasi up your bullies with a big-ass dragon.