"if watchdogs was released for wii u at the same time as the other versions and advertised what the wii u gamepad brought to the gameplay do you not think it would have a better chance at higher sales because it was advertised the advantages that the wii u could provide"
Sure, why not?
Else, if some games sell less on the WiiU, a good part of it is also due to very poor quality ports they sometimes make, either with worse graphs (and they have no excuse for that, 'cos to the games being released WiiU still has enough horsepower), either they make no decent use of WiiU's advantages, like the GamepPad sreen and gyroscope and even the free online gaming.