Timeless gameplay that doesn't live off of trends and current gimmicks as a main sales incentive. That's also the reason why Gran Turismo has such great legs and games like Baldur's Gate can be re-released and still do well.

Because they don't come out with a sequel for the system. If you want 2d Mario on Wii, you have only 1 option. So they keep it on the eye level shelf at full price. 3d Mario only had one game per gen until this one. 2d Mario the last 4 systems its come out on has been 1 per system. Same with Zelda except for the hybrid TP. MK has always been one per system same with Smash Bros. People want those franchises on their system and there's only one place to get them. Sony has only done this once that I can remember and that's with GT5 to a similar effect. Their games usually have a strong party focus for lasting value as well, at least that's why I get them (on ebay or Amazon at drastically reduced prices from the store). Zelda and 3d Mario are great SP experiences, but Smash, MK, and 2D Mario are great local co-op games with that lasting fun factor. Same with Goldeneye back in the day.

Joe the Bro possibly had the best answer in here.

When people finally decide to pick up their Nintendo Console, they'll want in on some of the games that came out earlier for the system. Every year more and more people buy a Nintendo console (obviously) so more and more of their SW titles, especially the popular ones, get sales.

not completely true after the wii and wii U, they popularise the motion gaming gimmick with the wii and they tried to get easy money with the tablet gaming craze with the wii U, but they do have games that don't follow trends with mario and pokemon

Wii Sports, Wii Play and Nintendoland belong to this category of gimmick driven games. Besides those, most Nintendo titles didn't really make heavy use of the Wii-motes capability at all, mostly waggle and some games were even best played with a classic controller (Mario Kart, NSMB, SSBB and Zelda, for instance).

The Gamepad as a gimmick to drive sales isn't working and won't work, the concept is entirely too weak and aimed completely wrong, Nintendo are being handily beaten on the touchscreen control by tablets and smartphones. The Gamepad was a horrible idea to begin with and the hardware and software sales confirm as much.

The Wii-mote rose quickly and was a really big hit, this was one of the keys but the main reason why Zelda, Mario Galaxy, NSMB and Mario Kart have such amazing legs and attach rates is simply due to the aforementioned timeless gameplay and reliance upon a solid core, playable structure rather than gimmicks and effects. As mentioned, the Gamepad will do nothing good for Nintendo, it might end up harming them in the end. If they make their games with the same philosophy as ever though, we should see some great legs for their main franchises in the 8th gen as well.

Can't say i disagree with you

Nintendo confirmed for the Fountain of Youth.

Fairly simple question. Nintendo games target mostly casuals and kids. The target aren't like us - they don't keep up with release dates which is why not all Nintendo games sales are front-loaded.

The other reason is that Nintendo systems suffer from long droughts which means that there isn't many options for people to choose from. It's easier for someone to buy 1 game from a selection of 1 than 1 game from a selection of 5.

Lack of competition and sequels. With the other consoles the successor supersedes the predecessor, meaning few people will buy Uncharted 2 if they are new to the franchise and can just buy the 3rd instalment. Also with a focus on MP, no one wants to get a game where the MP is dead as everyone has migrated to the sequel.

If they were "loved by the masses" then why has NSMB Wii U not helped push more consoles?

There are probably many reasons for this, including:

1) the strength of the brand
2) the high quality of the games
3) the fact that many of these games can be enjoyed by video game fans of all ages and skill levels