First appearance: More Fun Comics #55 (1940)
As DC’s resident expert in magic, Doctor Fate has always been the go-to guy for any hero looking for help against supernatural foes. When he's not surrounded by other characters, though, Doctor Fate fails to stand out on his own. With a face covered by his trademark helmet, the character's origins and personality have always been shrouded by mystery; because of that, he wouldn't work on film.
Fate's mystical comic stories have to waste so much time with exposition in order to get readers acclimated to his magical worlds that people's emotional engagements are left by the wayside. And when the main character hides his face behind a bell-shaped mask like that, any personal connection to him is impossible.