Have Your Say: What Is The Most Under-rated Superhero Film Ever?

All around the globe, Avengers: Age of Ultron is barging through cineplexes, the latest entry in the vast assault that is the Marvel Cinematic Universe. And while these films are undeniably popular, there seems to be a growing sentiment that there are now maybe too much of these films around already. With Marvel gearing up on Phase III and Warner Brothers aching to get a super-branched-franchise for themselves, there won't be a superhero dearth for several years to come. We may be heading for an overload.

Not so long ago though, there was a time when superheroes were considered pretty unmarketable film-wise. A film about a superhero was a fan gamble, with (some) mainstream attention being the holy grail to achieve. A lot of superhero movies from the past look pretty low-key when compared to the current crop of super-produced effects juggernauts. Many of these failed to make waves upon premiere, and were quickly forgotten by most.

That doesn't mean that there weren't any gems among them though. Some of these films have a distinct charm, or original implementation of the whole 'superhuman' theme.
In your opinion, what is the most under-rated superhero film ever? High-budget or low-budget, famous or infamous (or worse: forgotten), all are fair game, as long as you think they are unfairly maligned.

So chime in, in the comments below, and HAVE YOUR SAY!