So are we talking about this forum or public interest in general?
I believe that manga already gets enough recognition outside of AF so I don't really see any problem there. Comparison to books was a appropriate one and same could be said for pretty much any type of media. I don't think that books or manga are good or bad for anyone, you can't just sit through and read a book in order to understand it and gain something from it and same goes for manga. Personally, I lean towards source material since I like authentic stories but that's just my personal preference. That isn't always the case though and that's the thing, books/manga aren't always better than movie/anime.
Sometimes they go their separate ways like in Shaman King where anime series at one point surpassed manga and eventually had a completely different story development and ending. The weird thing is that I've liked anime ending way more than one manga had. Anime had a more simplistic approach and a straightforward story, while manga branched off in many different directions and it way too complex for its own good. Obviously I'm not saying that Shaman King anime is better than Shaman King manga since it's matter of personal preference, but I don't think that I would've liked series as much if I've only read manga.
Sometimes this can also happen with movies, Lovely Bones for example.
Just a quick disclaimer: I didn't read the book with this one!
So why am I taking this movie as an example then? I didn't like Lovely Bones for its amazing plot or characters or whatnot since I'm simply not a fan of the genre, only reason why I've watched Lovely Bones and liked it in the end was amazing scenery. That could've been accomplished in a book, I'm not saying that that's not the case, but during the whole run time it felt as if it was screaming 'THIS WAS MADE/WRITTEN TO EVENTUALLY BECOME A MOVIE!' since it was always supposed to be a CGI spectacle. I own the book and might read it one day so there might be an update later on.
When you think of Harry, Ron and Hermione you think of Daniel, Rupert and Emma. Emma in particular was the problematic one out of the bunch since she was way too good looking to play Hermione, which became more apparent in later movies when her character had confidence issues regarding her looks which didn't really came through in movies. Still, pretty much everyone fondly remembers these 3 as big parts of our childhoods even if they didn't remain faithful to the source.
With each new adaptations existing stories gain and lose certain aspects they've previously had and eventually become a stand-alone pieces of work. Books and movies won't ever be identical, or necessarily better than one another, they're different types of media with different challenges and complications to work around. Same goes for audiences since simply reading a book or watching a supposedly good movie won't necessarily guarantee that YOU'll personally have a good time or same experience as others. Being versatile and adopting best of both worlds (as Hannah would say) is indeed the best way to truly study any work, and the more mediums you have access to (affinity towards reading books, watching movies, listening to the music, etc.), the richer you are as a person.
Finally I'd like to see manga related threads under anime subforum rather than hobbies since two are closely connected and pretty much on equal footing, even on Anime Forums.