I think amiibo will play a role too starting on Wii U

3DS: Last truly dedicated handheld before Nintendo jumped into mobile and the unified handheld/console platform.
Wii U: Great games but Nintendo's worst selling console. That said, it laid the ground work for Off-TV play which was perfected by Nintendo's next-gen unified platform, the NX/Fusion.

Wait, what? No Zelda, no 3D Mario adventure, no Fire Emblem, no Paper Mario.

The legacy will be the book What not to do when designing videogame consoles.

Chapter I - Nes and how draconian grasp on third parties can pave the way for future problems.
Chapter II - SNes and how our kiddy image was born and third parties broke free.
Chapter III - The Virtual Boy and... oh forget it.
Chapter IV - We love cartridges.
Chapter V - If it looks like a lunch box than its our Gamecube.
Chapter VI - The Wii and welcome casuals... wait... are you leaving?
Chapter VII - Since E3 2011 everyone knew it was not going to work... except us.

Yep, I fail to see how the wii u is even at gamecubes level yet. Won't even be remembered as fondly as the little box at this point but who knows what games are still coming. 

3DS-Nintendos finest handheld in terms of quality software, and a solid seller despite the mobile gaming boom.
Wii U-The best versions so far in the Mario Kart, Smash, Donkey Kong and Pikmin series (hopefully Star Fox and Zelda too). First real open world Zelda, Amiibo success which so far is mostly associated with Wii U. Poor sales, but appreciated by the real Nintendo hardcore.

if you ask me it's already a better console than the Gamecube; it's got a better 3D Mario, a better Mario Kart, a better Donkey Kong, a better Pikmin, a better Smash Bros...

Agreed. GameCube is overrated. 

If Zelda U is better than Wind Waker, than it's basically curtains on that debate. 

All I will say is this for Wii U. For rare games buy multiple copies. Cause come 5 years from now they will be selling for over $100 each.

For me, not matter how stronger the mobile industry became, the 3DS fought hard and fought back with great titles. The Wii U will turn out to a console with rare treasures that people will most likely play a decade from now.