I'm gonna have to go with Sony.
Following past trends that Nintendo systems have followed ever since real, non-Sega competition came into play, the Wii was certainly an anomaly. Nintendo won't see that kind of success again, at least not with the Wii U, with how their systems generally sell. The only way the Wii U will pick up is if they cut the price because at $350, the Wii U will be completely slaughtered by the competition. As it stands, in a few years time, developers may be hard pressed to do better than lazy ports to the Wii U, if they're worth it at all, when considering the gap in hardware between the PS4, One, and then the Wii U. When you consider that supposedly the PS4 is so much more powerful than the One that differences will be noticeable out of the gate, that doesn't exactly bode well for the Wii U, being weaker than both. With that said, I don't feel the first party will continue to provide any sort of pull that will move more than maybe 30 million to 40 million systems on the outside throughout the life of the Wii U, and that's only if the third parties don't entirely abandon it. The PS4 has established itself as new, different, appealing, easy to access, minimal online fees (as nice as free is, if $5 a month gets better service + free stuff, sign me up), powerful, and the best choice for a developer looking to really do something amazing with the tools at their disposal.
I feel that Sony will get the third parties, the majority of the third party exclusives, and will ultimately sell far better than the competition. I think the PS4 will place itself among the PS1 and PS2 and break the 100 million sales mark, placing Sony back on the throne where really, it belongs.