Here is something to consider.

Steam does not advertise it's games except on it's portal.

Steam gets games LATE.

And yet they sell. Perhaps the issue is not the advertisements but is the fact that the games are not the same and are not offered for the same price on the Wii U.  Maybe the portal Steam runs just does a better job of advertising the games.  For me it's about the price.  Steam offers games for cheap several times a year in big sales.

No, they should NOT spend BIG BUCKS, but they should do some basic stuff that could cost very little. Here are some things...

-Include the console logo on their already created advertisement, is just an image added on something they already paid for.

-Release screenshots for the Wii U version in their press releases, just take a few and send them away

-Mention their exclusive features, like Miiverse interaction and Gamepad functionality even if it is minimal

Now they could reach to Nintendo (and viceversa) to be included as part of the Nintendo Directs, provide an exclusive trailer/footage and let the company show their games so the fans know about them.

Making some easy and cheap stuff they could improve the visibility of their games WITHOUT spending big bucks, because the ROI would be low if too much is spend on advertisement.

But PC sales are usually way less than console sales unless the game is pc centric also as you said steam usually has great discounts.

Yes to get more sales, but who are they selling to, if nintendo pretends that the wiiU does not exists why should 3rd parties pretend that thier is an audience there.

What do you mean Nintendo pretends the Wii U doesnt exist? I see them supporting it quite clearly.

Are you sure you're not confusing with Sony and the Vita?

They get sales when they treat the platform the same as others.
You can't really expect me to buy their stuff when 90% are gimped in 1 way or another.
And majority of the times, the price is higher. I'm not buying it on WiiU for $40 when I can buy it on PC (or other) for $5.
Releasing it later than other platform also cut in the sales. You don't expect people to buy the same game again when they already previously bought it.

The problem isn't so much that they are sending their games out without marketing. It's that they're doing it, and then claiming that the resulting poor sales demonstrate why they didn't market the game. They can either send their games out to die, or they can complain about poor sales of their games on the system, but they don't get a free pass to do both at the same time.

The 4 third-party games that have done decently - ZombiU, Sonic Racing Transformed, Rayman Legends and Monster Hunter 3 - have had effort put into them and decent marketing (although Monster Hunter 3 was only published by Capcom in Japan).

I'm surprised these publishers haven't noticed a pattern here tbh. If a title is on par with the other SKUs and not gimped in any way and is released the same time as the others and at the same price and with the same marketing push it'll make a profit. It's really not rocket science.

EA should re-market Need for Speed; Most Wanted on Wii U in advance of the NFS movie coming out. Cut the eShop price to $25 and do a limited restock of the game at retailers. Then pay a bunch of WiiU gamers/bloggers to promote it.

The game is out of stock at nearly every retailer and it's price has actually gone UP on amazon over the last several weeks.

I think it's not even that they don't push the titles, but that it's almost like they TRY to make them not sell.

The most simple and obvious case is COD: Ghosts. It's not like it needed a major push and was never going to be a huge seller, but Activision denied its existence for months, even though it was obviously in development for more than a few days. The Wii U logo was absent from marketing. It costs no more to include a little blue U in your ad spots than to not include it, so why don't they?

The only explanation I can come to is funding from MS and/or Sony; I've heard that Activision gets a cut of Live revenues, though I don't know if that's true. But the issue isn't so much about lack of push, but that 3rd parties are actually pulling on the success of their titles. The Mass Effect debacle is even more extreme, and there are others. But the subtle things like Ghosts make no sense.