If the Wii U had full support from all the major 3rd parties, would it have competed with the PS4?

[MajorMalfunction]

I voted no. The Wii U failed because in the eyes of many, it's an undesirable product. It's a console that's doubled down on Japan while compromising on the needs of the global market. It's design is focused on exclusively on Japanese needs (small, low power consumption, Off-TV Play), while the Japanese gaming market has migrated mostly to mobile. Not to mention Nintendo's own problems with releasing software globally, physically, and consistently.

Nintendo's 3rd party woes are real, and are a real part of the Wii U's failure, but there's more to it than that. IMO, no conversation has found why the Wii U failed commercially because the Wii U's problems are fractal. You don't go from 100m to ~15m without some fundamental rot in the core idea. Michael Pacter said that the Wii U, in his words, was "a crappy product." I disagree, I don't own one, but my cousin does. I think it's a well built, well engineered product that does what it does very well; it's just that no-one cares about what it does, they all want PS4s and XB1s.