Pretty sure the majority of people who have a Wii-U either has a PS3/Xbox360 and/or a decent PC.
"Incredible gamepad", that is debatable along with the fact it isnt really necessary to get the full fledged experience out of a game like Mass Effect which wasnt created using the gamepad to begin with.
"Plus 50 for all old games"? Where at....most games cost $19.99-$24.99 and a few of them will be $9.99 to $14.99 (and some for $9.99) during BF o.o. Far cheaper to get it on other systems especially the PC, if you are that desperate to play it, play it in low settings l0l.
tl;dr there are better games out there for the Wii-U than a shoddy port like ME3.