First off, are you German, or do you just like saying "bitte"?

Secondly, at the time of their release, all three games you just listed were considered some of the best games to ever come out. I personally have never been into ANY of those series, but I am able to separate my personal dislike for them, because they do not fit my gaming tastes, and my understanding that while I may not like them, they are still fairly well made, and that a lot of people like them regardless.

And I think you entirely missed my actual point, which I suppose is to be expected in this internet age of people usually not actually paying attention, just typing words. Allow me to rephrase. Twilight Princess, Brawl, and Mario Galaxy are some of the highest rated games, and most highly regarded games, OF ALL TIME. With good reason. THAT was my point. They are incredibly well made, extremely high quality, and FUN to play, hence they have a high replay value. THAT is why they have legs, and THAT is why people continue to come back to those franchises again and again. Because as consumers, we know that those games are usually a product we can trust to be a quality purchase, and not a waste of money.

Just because you might personally feel different, IE you might not personally like those games/franchises, I fail to see what bearing that actually holds on the thread topic, that being why big Nintendo franchises have such "great legs" when it comes to selling a lot and for a long time.

That's easy. First party Nintendo games are almost always one of the primary reasons people buy the console. This same sort of thing happens with all top consoles, it happened with the PS2 and GTA titles.

Gran Turismo, I think that situation is a little different, the game CAME with the system. I don't think many people actually wanted that one since you could get them for almost nothing at pawn shops. You can still go into those shops and see them available second-hand by the dozens.

The reason why some Nintendo games have good legs is: kids and casuals. Especially Mario, especially on the 3DSDS. The reason Zelda and Fire Emblem don't is because they don't like them as much.