I'm 31, and I have no problem telling anyone that I'm a Nintendo fan (being one since the original NES). I don't need the approval of society to enjoy what I do. I didn't need it when I was around 13-14 and some people made fun of me for watching Power Rangers. I didn't need it to enjoy Sailor Moon around the same time. And I certainly don't need it now that I'm an adult. Fortunately, I'm perfectly capable of thinking for myself, and thus I do. As the old saying goes, live and let live.
The best thing the game industry could do to get respect from the "mainstream" is to follow its own path. To not let the opinions of those outside of it dictate what it should be. To not be reduced to imitate other established media for the sake of approval. And of course, to have a wide array of offerings to choose from, as every medium should.
