Looking at the tail on 3D Land, I suspect this will beat out Sunshine eventually --
providing they don't let the system stagnate below 10k again next year

Biggest thing hurting Wii U right now is 3DS. I have to agree with posters on GAF that said this is similar to what Vita initially experienced in terms of perception... GOW, Uncharted and the like weren't different enough to make it move. Even after eventually correcting that, Sony have struggled to sell it. Its only now that it is gradually becoming healthier - in Japan at least. Wii U doesn't have a tearaway, layton, pullblox, kid icarus, luigis mansion 2, etc. Minor unique experiences might be as important as big exclusives. All the big games so far have been really iterative, at least in terms of how you would perceive them at a glance. I also agree that Smash 3DS is going to hurt the impact of Smash Wii U.
People asking for 2D Metroid (and the like) are bonkers if they think that'd help sales, as the system has plenty 2D platforming, but a Metroid of some description would be nice. I really hope their next software tranche is more daring than what they've done so far. The other 2D platformers (DKCTF, Yoshis Yarn etc) aren't going to do shit to help.