Well, the kids started out with several games: Zoo Tycoon, Ryse, Killer Instinct and Forza 5. On the PS4, they are hooked on Lego game plus Contrast.
Resogun (PS4) is still the most fun on either platform.
That said, my kids spent most of the day on the WiiU because of an annoying factor with the XBOX One.. every time my wife would say to the kids "do you like the XBOX?" or anything where she mentioned 'XBOX' the screen would pop up asking them what they wanted to do, etc. Just a real 'uhh..' kind of moment.