of course the better games thing is debatable. but as far as power, online, features and the overall hardware goes, PS4 and XB1 are superior. 

1) Why are more people buying PS4 and XB1?

- Popular 3rd party franchises, features, specs, marketing, etc. and Wii U's pricing is not so competitive.
- PS4 and XB1 are perceived as new and exciting.  Wii U wasn't able to build momentum early and even average people see it as a bit of a failure.  It's not able to build enough excitement around it's big titles (except in biggest of fans, but they have Wii U anyway).

2) What do you think Nintendo could do to turn this thing around?

Price cuts could help, but it's likely that they just aren't able to make enough games to maintain momentum.  I think they've settled for just trying to please fans and not lose money while they work on a future platform.

I think if they want to make money they should go multiplatform until their next console is ready, but if they are OK with current financials then they can just ride it.

I think the whole family/"more kid friendly" console idea is simply kinda destined for third place in the modern market.

Consumers kinda had their "vote" on that during the Playstation 2 vs. GameCube and showed that they overwhelmingly chose Sony's vision of game console's being more like "serious" electronics with media capabilities over Nintendo's approach of a more "toy like" console focused on gaming with a heavy dose of Disney-esque franchise properties.

Nintendo's just never going to win with this formula in the console business, because even kids don't support it, they want what the Sony model, not the console their mom would buy for them (by the time kids get to age 10/11, they desperately want to play what older kids are playing).

Ultimately Sony's vision for what a home console simply won over Nintendo's vision and it did so a while ago. People just moved on to that. Nintendo is kinda just running into the same brick wall ever since.

Nintendo just can't "win" with this formula. If it was 1994 maybe but it's 2014. 

Why not sell it?  It's not like a collectable for many people.  Online multiplayer games are good for hundreds of hours while people keep playing them.  After people move on it's no longer as fun as originally, so why keep it?

Let's have a look at Nintendos options, shall we?

More (and maybe different) Advertising? Nintendos main problem is it's image of being "Kiddie" and "Casual". Once Children hit Puberty, they defenetly don't want to be associated with any of those, so they switch to Sony or Microsoft, and generally stay with them. No amount of advertising will be able to change that.

More mature games? Didn't work, neither on the Gamecube (Metroid Prime, Resident Evil, Perfect Dark...) or on the Wii (No more Heroes, House of the Dead: Overkill, Mad World).

Buy IP's? Yeah, just look at all the comments on Bayonetta 2 (not just here, browse around the web). Most of them go like "I'd totally buy it, but only on a non-Nintendo Console" or some variation of it.

Drop the Gamepad? Apart from the fact that many games actually require the Pamepad's second screen in one way or another, what good would it do anyway? Basically what would be left is just an massively underpowered PS4/Xbox ONE with less games to boot. The console could get cheaper, but as some have pointed out already the Gamecube sold for much of his at a 99.99$/€ pricetag and it didn't help it either.

Get back the multiplat Publishers? They dropped out basically because they could afford it, as their games just didn't sell on Nintendos Home Consoles for Generations. The Wii was a must for them due to huge amount of consoles sold, especially until 2010, but otherwise they would probably already have done so in the previous generation.

Develop new IPs? They already do so (Splatoon, Mario Maker). Half the time however they will just be B-List games because of underwhelming sales, like F-Zero and Metroid did most of their time (and the reason why there might be none of them coming out on the Wii U), just like most Mario Sport titles (also none yet on Wii U).

Basically, Nintendo is pretty much at Morton's Fork, meaning whatever they do, they can only do it wrong for most people.

Wii U draws critical praise from many publications. Time, Forbes, hell even Fox News is spreading the word about Wii U. It is free publicity and it is good publicity. Nintendo's biggest struggle was getting people to knock it off with the Wii U is doomed articles. Now that the Media is finally on their side they will have one less enemy to worry about. Nintendo just needs to survive this generation, and they are doing that well.

Nintendo is in a transitional phase. They are moving their developers into a new building and are consolidating their console and handheld teams and moving their support staff there as well. When they are done with the transition they will be pumping out the games at a break neck pace and Wii U and 3DS won't have the droughts they have had.

Eventually people will finally run out of excuses to not buy a Wii U and will join the party.

Here My piece of the Pie.
Why are people buying ps4 and Xb1? Simple because those are the one that play the 3rd party games and follow the norm. Let be real, at this point in the gen ps4 and Xb1 are are like coke and pepsi. They Both offer Almost the same libary of games and are spending a lot of money on advertising there systems. Think of this as a Round 2 between Sony and Microsoft. Lets not forget the brand loyalty people may have with these two companies.

What do you think Nintendo can do to turn this Thing around?
Nintendo Finacially Speaking are in Good position right now. They Profit off Every system and They get the most profits off there games. The Also Nintendo remain the king of Handhelds. As far as Wii U goes i dont think there gonna penetrate the Market enough to win but to be fair i Dont think ps4 and xb1 are gonna hit high numbers either. What Nintendo Needs To continue Doing is making there first party games since it is after all their Strength. I will be honest as a Nintendo Fan im somewhat Dissappointed that the Wii U is unpowered and unfriendly to 3rd party in which drove them away. What They NEED TO Do is Simply Prepare for Next Gen. 
Nintendo is the only one of the big 3 im looking foward for next gen simply because they got the balls (lol) to try something new. The Gamepad was never a bad idea nor does it hold nintendo back, it simply hasnt been fully utilized.  If Nintendo Can make a powerful enough Console where it holds its own against the other two, while being developer friendly, while improving there online, Improving Gamepad functions, and Still make There First party games thrn they can win 9th gen with there eyes close. 
If Wii U were to be just as powerful as xbone  and have full support the 3 party games the other two have, would you guys consider getting a xbone or a ps4?

Another person who wants to bring down Nintendo.

Nintendo should switch their focus from hardware to software. As a software company Nintendo would be bigger than ever before.

nintendo going forward will have low selling consoles but games that could sell boatloads. I've always said that for nintendo to stay relevant they needed to invent the handheko themsekves back when it came out. They were too stubborn to enter the mobile market then and prob didn't even dream up a device anything like it. Sadly for them at the time the DS was on it's way to be the second highest consoles ever. The iphone caused a major shift and even if they straight away partner with google and made a rival to the iphone they'd be in a better place today. 

Either they try break into the market now whixh is very hard or they go software and rake in millions. Pokemon and the like would make ridiculous money on iphones and androids especially in japan. They have a long console history so it must be too hard to let go. It will be their downfall if they don't. ANd how will that bother 3DS fans? Most of you anyway will have a smartphone or could get one as a result. You'll still get your games and nintendo will make even more money. 

As for the home console. The Wii was a fluke thanks to the motion controls. That has come and gone. Gamecube and Wii U are their natural level of sales and with Sony flying so high and MS willing to spend crazy money to stay relevany I can;'t see them squeexing back in with a traditional console. If they want to sell big numbers again they need to dream up another fad. THe obvious answer would be VR but SOny, Facebook and MS are all a few steps ahead there. 

Maybe their next console will be an Oculis rift type thing and it will capture the worlds imagination once again. I just don't see it happening.