I still think if they want to go beyond the regular Nintendo fans, they need to rebrand some of their ips.
The funny thing is that i see lots of people here screaming their Pikmin love for example, but hey.. You ARE the Nintendo fans, or at least you bought a GC. People who bought the NGC are basically the core Nintendo audience i think, and that's already a lot. But that's not enough to be first, if you don't have a blue ocean to back you up.
In the end, Nintendo's demographic didn't really change and the problem is still the same. The guys who shifted to Sony and Microsoft, or even debuted with them. I'm not sure they can be bring back in. But if Nintendo wants to do so, they'll need a great online environment, and especially ips with dudebro impact.
Those could be :
_A mature, dark and realistic Metroid with Crysis quality alien environments and interactions + an actual awesome art direction.
_A Wave Race with never before seen water physics and shaders and some impressive settings (like you know, a storm with the light of a lighthouse, this kind of things) and some great music (oh and a great gameplay of course

)
_Same for F-Zero after that. This kind of game is just ideal to show off next gen visuals. When you think about it, last time we actually saw a Nintendo ip with never before seen graphics was 10 years ago.)
_About Mario it's tricky, not sure the dudebros would even go for it anyway, but as far as i'm concerned, i want a Mario which try to impress and be magical, ala Wind Waker for its time. Nintendo can go fuck itself with the "Mario is just about gameplay man" mentality. When i was a kid, Mario World was like playing a cartoon for christ sake!
I know i know i'm a graphic whore, but it's also a matter of cultural evolution for Nintendo.
Also graphics ARE important, and the contrary talk is wrong for me. i've got my theories on this subject. I strongly think Video game are not games, and they are, in their core definition, not only you doing things, BUT You doing thing through an artistic representation. That's what they are and what they always have been, since the first time. Pong is an exception in that regard. Representation of an action is 50% of a videogame, but anyway....
Nintendo has to work on all that.