Every Mario game after 2010 sucked balls, just sayin'. But they're not dying at all.
Oh, and the Wii U will become popular once they release Super Smash Bros Universe, Mario Kart U, that new 3D Mario game, Zelda U, the Pokémon game, Wind Waker HD, etc. Wii U did have a crap starting line-up, and the loading times are terrifying, but they're releasing an update soon, as well as all those games I just listed.