"I, for example, have never bought a non-Nintendo-published system or game."
I don't know if this is a better example of Nintendo's software development capabilities or for Nintendo's inability to get third-party developers on board.
You could really take the best 4-5 games on each Nintendo console and you would have Nintendo only titles. This doesn't work for the PS3 or 360. Here the really great titles are generally third-party. And for loyality? I have a PS3 because the hardware is much better than the 360 (RRoD, looks, media capabilities, included WLAN...) but if the 360 gets really really cheap and won't destroy itself anymore I might get one to play Halo3 and Mass Effects. I think people who don't buy games just because they are not from their personal Developer are stupid.