The thing is, while Wonder Woman is an cultural icon, The Flash is only an icon to fans. Yes, he's famous enough that pretty much everyone knows who he is, but he doesn't represent anything essential the way the big three do. The Flash, to us, is all about family, with even his rogues forming a fraternity, and these are things we as fans can appreciate. Wonder Woman really has none of that. She presents an image of strength, beauty, and confidence to a world that has never read a book in which she is featured.
Much more so than the other icons of the industry, her image to the public at large is much better than the reality known to the comic book fan. Her personality is poorly defined, her history and origin is an ever changing mishmash of cribbed Greek mythology, and her rogues range from pathetic to forgettable.
That said, she's still a comic book character with 70 years of history, and no character with that much history can be completely without good stories.