It will leg out over the next few years and pull in good enough numbers, many will pick it up when they arent overdosed on platformers and need a platform fix.

I found Donkey Kong Country RETURNS on the Wii much harder. And that sold better.

So in my opinion its simply the installed base...

I don't think they make to many platform games.

Wii U only has SM3DW, NSMBU, Rayman legends, DKTF, and a handful of indie platformers ranging from great to mediocre. It might seem like a lot next to other systems but that's because they have no games.

What's with all these alts?

Nobody owns a Wii-U so it cannot sell well. And I would not have bought it because it misses the Rareware magic and perfect music of the classic DKC-Titles, I did not like the first DKC Returns at all, it was just a bad game with way too much motion control bullshit in my opinion. DKC2 is my all time favorite Jump & Run by the way.

The platformer issue has already been addressed...
But there is also the issue of the general public being unaware of the Wii U's existence, and this being unaware of the console's titles...
Though I don't think half a million is bad on such a small install base...

There's also the fact that DCK was a technological marvel more akin to what will be the best looking PS4/X1 games in the next couple of years. Although "only" a 2D platformer, back then it was the business. First game to have CG rendered visuals, which were actually being called 3D at the time because the game was full of 3D renders for the models and backgrounds. There was a hell of a lot of exposure for it at the time, entire sections of TV shows documenting the techniques used to make the graphics etc on prime time TV. It had a lot more buzz.

Tropical Freeze is pretty, but it's "just" a 2D platformer rendered in 3D now. Plus the British just make better games :p

Chuck in the low userbase and current oversaturation of platformers (particularly in comparison to other genres on Wii U) and I don't think it was ever going to do the numbers some were expecting. When Wii U gets down to a mass market price and a bigger audience comes, I see it continuing to chug along for the next few years though.

No. It didn't sold well because nobody asked for this and sales proves it. It was a mistake to release it and after announcement most of us were dissapointed. We ask for a real 3D game that push Wii U to its limits, I don't have an HD platform to play a Dk 2D game.

I think the argument is that they played DKCR (since it sold 6 million), but got turned off by the difficulty and so figured they weren't missing much with Tropical Freeze, if they even knew about it.

I think there are plenty of other reasons contributing to its slow sales.

it will sell over time, dont panic...