I think Super Smash Bros U will sell more than Uncharted 4. The reason being that Smash is a bigger franchise. The Wii U will certainly hold the game back from reaching it's full potential but let's not forget that the game also comes out for the 3DS.
EDIT: Oh It seems that you only take into account Super Smash Bros for Wii u sales. Then yes, Uncharted 4 will outsell Super Smash Bros U.
"I've Underestimated the Horse Power from Mario Kart 8, I'll Never Doubt the WiiU's Engine Again"