Marvel's decision to put the power of Thor into a woman's hands may have been greeted with derision or open hostility by a pocket of their audience, but nine months out from when it was announced, the first five issues of Jason Aaron and Russell Dauterman's Thor have sold over 100,000 more copies than the last time the character had a renumbered solo title, 2012's Thor: God of Thunder.
A note on the names relevant to this article: When Aaron and Dauterman's series was announced in July, they surprised and confused many by being very clear about what their new character would be named. She wasn't Lady-Thor, Fem-Thor, Female-Thor, Thorette or any other feminized variation on Thor Odinson's name. She was simply Thor. And so was Thor (He's currently referring to himself as Odinson and adventuring with a magical axe named Jarnbjorn until he can be deemed worthy of wielding Mjolnir once more). One of the ways the creative team "enforced" the naming convention is simply by not giving fans anything else to call their heroine: the central mystery of Thor is, who was its titular character before she lifted Mjolnir and was deemed worthy of possessing the power of Thor?
The most recent Thor #1 sold 150,862 copies, based on ComiChron's numbers (which in turn are based on publicly released sales figures from Diamond Distributors), while Thor: God of Thunder #1 sold 110,443. First issues of a new series always sell significantly better than those that follow because they are considered to have a higher collectible value, but even by issue five, Thor is still selling better than Thor: God of Thunder's #5, by nearly 20,000 issues. You can check out a handy graph at Fusion. None of these numbers include digital sales figures, which as yet are not regularly released to the public by Marvel Comics or any digital comics retailers.
There's a legitimate argument that entirely new female or racially diverse heroes need to be added to superhero universes, not simply as race- or gender-swapped "legacy characters" to a more famous hero who will inevitably eventually return to the name and title role. Entirely original superheroes without connections to long-running established characters, however, have a tough uphill battle in the small market for comics, and it's much more likely that a series will be able to maintain good numbers if it can piggyback off a recognizable name. Even then, things can never be certain. Storm and Black Widow are two of Marvel's best known female characters, with major movie franchises under their belts, and their ongoing series are both ending soon.
A frequent fan reaction in some circles of the established audience for comic books is that companies are "pandering" to a "vocal minority" when making comics about or for women, especially in cases like Thor, when a female character is swapped into the identity of a male one. It's a reaction that is more and more frequently being called into question by the undeniable success of Thor and other books like Batgirl, Ms. Marvel, Lumberjanes and Bitch Planet that are not merely led by women but outright looking for a feminine audience.