I'd say it really depends on whether you can quickly purchase these consoles in short order if you want them all. If it's going to take you a long time to buy all three then I would recommend just looking at the upcoming games and see what tickles your fancy or look back to the previous generation to get an idea of what to expect even though it won't be 100% accurate. Do you like what you see of Mario Kart 8 and X? What about Titanfall and Fable Legends? Perhaps Infamous: Second Son and The Order: 1886? I'd say it all depends on what longterm titles cater more to your tastes.
If you can buy them all quickly but just want to buy the one that gives you the most value for money spent, I'd say buy a Wii U right now. Neither the PS4 nor the X1 will have a software lineup that makes the money spent worth it until about a year from now. There will no doubt be great games and I'm sure plenty of people would argue that one game in particular is worth hundreds of dollars. Realistically though you want the console that has the most quality titles to offer as soon as possible and since the Wii U has already been out for a year I'd say you have better options with it.
Super Mario 3D World, the Wind Waker HD remake, Pikmin 3, New Super Mario Bros U. All of those being among the highest scoring exclusives thus far. Not to mention some good third-party titles like Rayman Legends, Monster Hunter 3, and Injustice. You will simply have better options for the immediate future going with the Wii U. However, by this time next year both the Xbox One and PlayStation 4 will be loaded with games while the Wii U appears to have a very limited amount of new games coming.







