Casual gaming isn't blue ocean anymore. It's the very definition of a red ocean market. That's the problem. It's an overserved market with a million options today, many of which are free or $1 a pop.
That's a dead end for Nintendo.
The Wii U is not some core console (yet), look at Nintendo's freaking software allocation for the system:
Bridge games (casual friendly): NSMBU, Mario 3D World (2)
Casual games: Nintendo Land, Game & Wario, Sing Party, Wii Sports Club, Wii Fit U, Wii Party U, Mario & Sonic Olympics (7)
Core games: Ninja Gaiden 3 (port), Wonderful 101, Zelda: Wind Waker HD, Pikmin 3 (4, only 2 of which are new games)
Kids-centric games: LEGO City (1)
It has more casual games/mini-game compilations in year 1 than even the Wii did. The GameCube had considerably more "hardcore" exclusives early on ... Resident Evil Remake, Star Wars: Rogue Squadron II, Pikmin, Smash, NBA Courtside 2002, Wave Race: Blue Storm, Eternal Darkness, Resident Evil 0, Metroid Prime ... Wii U is not the GameCube. It may sell like the GameCube but actually looking at its software library it's probably the most casual-centric first year for any Nintendo platform ever (Wii included).