It's the same tired excuse, look at Splatoon which managed to sell great dispite the small amount of people that own a WiiU. If anything the lack of titles the WiiU was getting only helped Bayo 2 sell seen as no one had anything else to play on the console. Besides when Bayonetta launched on the ps360 there wasn't anywhere near 160 million consoles sold and the fact that the ps3 version which was full of bugs and nearly unplayable beat Bayo 2 is laughable.
It's really not though. When you look at how last gen was huge in terms of the Xbox 360/PS3 userbase, games like CoD and other tirles sold huge and were very popular, but when Bayo arrived, the game basically struggled on both systems to sell very well. Only when you combine both numbers does it start to look adiquatem but even then that's you having to actually combine them, if you look at them side by side, the numbers are pitifal for both userbase sizes.
Don't even know why on earth we're bringing Splatoon into this, especially since that game wasn't on last gen systems or even the Wii for that matter.