It would have been harder for Nintendo to market thanks to the success of the Wii riding on the novelty of its uniqueness.
Nintendo did push the GamePad pretty hard as the reason for upgrading; so much that it actually caused confusion amongst consumers as to whether it was a peripheral upgrade or a new platform initially. They didn't even show the box at first for those who have forgotten.
Maybe a better question would be "If Nintendo had utilized the resources and hardware costs of the GamePad in the console itself, would it have performed better commercially?"
Not sure if the whole hypothetical "If Nintendo had spent a buttload of money on hardware specs that rivaled the future specs of the PS4 and sold it for $400 would it have sold as well?" question even matters.
Nintendo would have picked up more sales from current PS3 and XB360 users, but would have lost the audience they captured with the novelty of the Wii. In retrospect, it looks like Nintendo lost most of that audience anyway.
The GamePad was a daring idea; slightly riding on the coattails of the success of tablets in the consumer market, but as it were, lighting didn't strike twice for Nintendo and while there are many Nintendo owners who love the utility of the device, it's pretty fair to say that it has not been selling nearly as many consoles as Nintendo would have liked or even as many consoles as they had projected.







