X1 is being outsold because it's too similar to the PS4 while the Wii U is unique in its offering, when people look at the new consoles they'll just get a PS4 to cover all the bases while Wii U has a library you can't get elsewhere so is a capable console in any situation.

Unsure why people treat 3D World as thier "big 3D Mario" or dont expect them to make another.

Im sure there will be another one, but yes its a 3D mario.

Wii u is directly competing with ps4 and xone.

yeah its been 10 of the last 12 weeks Wii U has outsold Xbox One

Different reasons I could think of, because I really don't think it can be explained by only 1 factor :
- a console sells better on its 2nd year, giving a advantage to the year ahead Wii U
- the ps4 is "stealing" more potential buyer from the XOne which has a pretty similar target
- the Nintendo public has more fidelity (I think)
- last but not least, Mario Kart not only performed very well but also clearly shows "you will get good versions of our best exclusivity". MS would get a similar factor from a great Halo/GeOW, but not has much as it's less 1st party driven
- it's less expensive

I don't see any reason for that to change in the next few months, the gap should even increase for Christmas.

No its not, not that its a good thing but its not.  

I meant like 64 ir Galaxy, though I realise it doesnt make a difference how the game is done now

I know the handheld market works a little different than home consoles but in term of 3D mario, 3D Land is the 3rd bet elling 3D mario.

1. Super Mario 64 - 11.89
2. Mario Galaxy - 11.09
3.  Mario 3D Land 9.57

And it's closing the gap with the Vita. Nice Wii U, nice.