How many 2D Mario games are there on home consoles since Super Mario World on the SNES? Only 2: NSMB Wii and NSMB Wii U, and we'll probably not see another 2D Mario game until the next-gen portables and consoles.
The only reason why people complain about NSMB getting "milked" by Nintendo is because of the fact that NSMB was released on the 3DS and the Wii U at the same time, without realizing that these are different platforms.
Zelda is another example. Windwaker, Ocarina of Time, Twilight Princess, Skyward Swords are completely different games on their own rights. Now the new Zelda for the 3DS will use a top-down view like the first ones. The last Zelda game nwith a top-down view was 4 Swords if i recall correctly, which was released almost 10 years ago.
The only thing i do agree with is that Nintendo needs to develop some new IPs. The last good IP Nintendo made was probably Pikmin. It's time for something new. But i don't agree with the idea that they are milking their core franchises. In fact, i actually think it's time to bring some franchises back, like Metroid, a 3D Donkey Kong like the one made by Rare, F-Zero, Mother (Earthbound) and Star Fox.