An interesting viewpoint you've got there. Certainly games like The Godfather, Manhunt 2 and Resident Evil 4 are there to prove its not solely a childrens console, but I do concede that its a commonly held belief. I find the same people usually also believe that mature games equals violence and swearing, which again, I find somewhat misleading.
As for the ancient graphics comment, I think thats an overstatement. It's at least as powerful as the first Xbox, which held some truly beautiful games. Of course, it'll never be as powerful as the 360 or the PS3, but I cant really say I want to spend a grand on high-definition equipment just to appreciate the "next-gen" of my 360. And admittedly nobodys truly fully utilising the horsepower of the console yet. It seems like Metroid Prime 3 is looking like it'll be the first to actually start pushing the console instead of housing lazy PS2 ports which do look pretty dire. And it's not like Nintendo have entirely dismissed HD tech. They've said they will probably embrace the technology into their next console, when HD gear is more affordable.
I admit the controller is not what I would prefer. Most surveys of gamers do seem to suggest that they believe that motion sensing is here to stay though, so I guess it may become something we all have to get used to. Heck, even Microsoft is now considering it. Indeed, sales of the console havent exactly died down, but I do think there's a serious lack of quality control at the moment, hence people labelling it as a novelty and a gimmick (and in some games cases, rightly so). If the quality doesnt improve for Christmas, I do think it may start to have serious adverse affects for Nintendo.
Not that I suspect Nintendo will be phased. The DS has certainly succeeded. Nintendo have even commented they may finally retire the Game Boy name now...