Hahaha, I love this analogy.  I've always thought MicroSoft was trying to be Hollywood, Sony was trying to be MTV, and Nintendo was trying to be 80's Nintendo all over again.

It's all about growing your product. Word of mouth, extended advertising, and building titles that have universal appeal. Local multiplayer probably has something to do with it, also, though it wouldn't explain games like New Super Mario Bros

It's a broad set of factors that come together that probably are unique to Nintendo, but not factors that can't be emulated

Retail.  That is the answer.

Retail will buy Nintendo published titles by the truck load for over a year but are nervous as hell buying any other publishers Wii titles - unjustly so.

ALL OF YOU ARE WRONG, reasons to "evergreen" are these:
1.- Lack of quality on 3erd party games, they leave open court to Nintendo makes everything they want.
2.- Publicity: Nintendo still making sales campaing for games released some time ago, and the people keep buying them, the best example it´s mario kart DS.
3.- Games of quality: Nintendo makes games with much quality, and their tittles almost never ends in the SECOND HAND MARKET, giving more oportunity too keep good sales, meanwhile crappy games from thirds doesn´t have this luck.
4.- Exclusive titles: Nintendo just make games for Wii and DS, meanwhile others companies don´t make exclusives for Wii, an d most of them are really bad games, or ports from old games, this strategy never goes to work.

Probably due to their broad appeal, Nintendo's marketing of them and the lack of competition.

I think any must have game for a console has this evergreen property. It is just that nintendo makes a lot of must haves which is because they have long established franchises that many gamers love.