Superman for the movie
Warner Bros. dumped The Iron Giant into the crowded film landscape of 1999 with terrible promotion and minimal confidence, letting it wander off to be ignored like a neglected ginger in a mall. Brad Bird's Cold War-era story about Hogarth, an adventurous boy with an unfortunate name who discovers a robot in his backyard and tries to keep him, was rescued on home video thanks to scenarios like: "My kid likes robots. This has a robot in it. It's five bucks on VHS in a bin by the checkout counter. Why the hell not."
Then the film, full of so many amazing moments that every viewing is like a tiny miracle of storytelling, works its surprising magic and (so long as you're not a Cylon or a Replicant or some sort of lizard person) you wipe your eyes and snuff back your last sniffle and smile at the great time you just had.
So the conventional wisdom (which is almost always broken when it comes to Hollywood) morphed from "It's a plain looking trifle" to the following lofty-yet-heartfelt sentiment:
"Iron Giant is the best Superman movie ever made."
I understand that sentiment. Especially in the face of divisive films like Superman Returns and Man of Steel, not to mention the confused Superman III or the earnest shoddiness Superman IV. It's easy to look at Iron Giant and say "That's what I'm supposed to be feeling when I watch a Superman movie."
It's better than that.
To get the pedantry out of the way: Superman isn't a character in The Iron Giant. "Iron Giant is the best Superman movie ever made" only works if the alternatives are so poor you're willing to settle. Not that "settling" for The Iron Giant is a bad call, but this is the first and most obvious stop.
It does fit on the face of it, though: a literal man of steel from outer space who, through the kindness of caring, open-minded folk, becomes a protector of humanity. But the Giant's journey is not the focus of the movie; the Giant isn't the main character. Hogarth is the one we're invested in, his arc is the one most developed, and his acceptance of what the Giant has to do is why the the film hurts so good.
(Aside: I've seen some argue that you can easily say the Giant is also a stand-in for the T-800 in T2: Judgment Day, providing a gentler spin on Cameron's story of a boy and his homicidal pet robot stopping a nuclear apocalypse. I don't really like that reading, but it's not without merit.)
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