One major advantage of manga and anime over American comics and cartoons is the spectrum of genres they present. Whereas traditional American comics focus on the exploits of superheroes, manga allows for a vast array of genres. Although most of the most popular mangas, which are eventually adapted into anime, revolve around fantasy battles, some mangas are decidedly more grounded.
Even though superheroes dominate at the box office, the grounded nature of several animes could result in an IP that's a better fit for the world of cinema. A manga like Kaiji: Ultimate Survivor, which follows the exploits of a gambler, isn't encumbered by the fantastical elements and pricey special effects needed to bring superhero fiction to life on the silver screen. Consequently, the inverse is also true. Some classic films could be adapted to manga and anime without losing too much during translation. In the video linked above, you can watch what the opening credits for an American Psycho anime would be like.