What exactly would it take to make Panther and Storm top-tier characters...not only in the Marvel Universe but in society's collective mind?
What would it take to make society stop and say "Wow...Panther and Storm are cool!"
I think Storm is, as an X-Man. I knew a girl who only read the occassional comicbook and Storm was her favorite character. But, many characters defined by being a team member struggle trying to get established as their own character. A chief reason is no built in context and supporting cast once the super-team aspect is removed. Look at the Thing. One of Marvel's most beloved characters and favorite member of the FF. But the only way he could hold onto a book was as a team-up book. The FF is his supporting cast,his family and his best friends. It's hard to do a Thing book without making it by default an FF book. Storm's history and reason for being is as an X-Man (and now as Mrs. Black Panther I suppose, I haven't been following her recent history), why would she fight crime as an individual? It's sorta like why would a policeman ALSO be working as a private eye? But, of all the "New" X-Men, Storm is about the second most recognizeable after Wolverine. A lot of that is due to Claremont's work on her as a character.
Black Panther should be. His all black costume is very iconic (which today's artists don't seem to grasp in their quest to clutter up simple iconic designs). And, he's fairly historically significant. Ultimately, I think his problem is about the same as Namor and Aquaman, and even Nick Fury for a while. Their day jobs as monarchs and head of SHIELD means each story has to justify why the are the ones going after the bad guys. Nick Fury as an agent of SHIELD makes sense, head of SHIELD not so much. It's why stories routinely dethrone them and take away their seats of power. You have the other wrinkle that goes along with him being a monarch, his stories by default need to take place elsewhere. In the 30s and 40s and even into the 50s, heroes adventuring in Africa were popular, today not so much. It's a hard sell in comics to have adventures that are not firmly in USA, even ones that are as highly fictionalized these days as the DCU and Marvel U. But, with most of the actions and adventures in a continuity-driven universe happening in America, his remote location is another hurdle to have to overcome, a problem all foreign heroes have. Not to say it cannot be done. But, the track record isn't really all that good.
Who knows, DC bringing back the Milestone characters may help the Black Panther and Storm, IF DC does some actual marketing, press releases OUTSIDE of Newsarama, comicbookresources, etc in efforts to bring minority readers into the comic shops, to tap into new markets and readerships.