I hate raining on parades but I feel some 104 style corrections are in order.
-Wii U and Xbox 360 have similar architecture making ports between the two easy, the main reason Wii U hasn't got 3rd party support is because of terrible software sales.
Only Iwata and maybe Tanaka thought the Wii U had a similar architecture to the 360 making ports easy. In reality though they are similar in total power, the 360 is a CPU heavy and GPU light architecture while the Wii U is a CPU light and GPU heavy design. Games designed for the 360 made heavy use of using the CPU to make up for the GPU's weakness, that doesn't transfer to the Wii U easily without a lot effort.
The memory setup is also different with the 360 having a single half gig allocation at higher speed while the Wii U has 1 gig of slow memory and 32 MB of very fast memory set up, again though roughly equal, code doesn't transfer over without major effort. Then there's the programming language with MS being as good as it gets and Nintendo being so bad developers didn't originally know they had to assign CPU cores which is something that was done automatically on the 360.
The poor software sales are indeed one reason 3rd parties quit, but if it were as simple as running the 360 code through a translator and doing a little bit of work we would still see those games regardless of sales (as we are seeing with indies where Unity is basically that).