All numbers according to VGChartz database:
Wii U has sold 6.1 million consoles and 23 million retail software. (Ratio = 3.7)
PS 4 has sold 7.2 million consoles and 16.3 million retail software. (Ratio = 2.3)
Xone has sold 4.4 million consoles and 12.5 million retail software. (Ratio = 2.8)
With one year head start Wii U owners buy more games but as it seems they prefer first-party.