As someone who just noticed the thread, and read the OP and will take that at face value...
...there is a question of "gaming literacy", sometimes discussed, much like reading the classics. And there is a fair point to be made in the reading of original ideas and the genesis of a style or method or genre.
Having said that... oh boy, this might be rough... but since the N64 I havent invested too much in Nintendo systems, and I don't think I've missed that much.
To be sure, I've missed some real gems. Of that I have no doubt. But I have played a fair share of GameCube and Wii just not my own and for my own particular tastes, there's a scant handful that I truly regret missing. I haven't played any Super Mario Galaxy. I regret that. Nor any No More Heroes (although that is coming to PS3). There's a few like that. But not very many.
Now, if I had to give up stuff like Wipeout, Uncharted, Mass Effect etc I'd probably open a vein. But that only speaks to my own particular peccadillos.
So to answer the question... I feel I've missed a little, but you can't catch everything, and this is mollified by the fact that I've been gaming since 1979, so I don't exactly feel like I'm not well-versed in the basics.

I played Great Giana Sisters. I'm fuckin'
legit.
I do find the Nintendo nostalgia very interesting. It's powerful.