The problem you have at this point is that major third parties don't WANT to support Nintendo. They want as much money as possible for as very little work as possible. Sony and MS have essentially bent over and grabbed their ankles for third parties because without their help both of them die off quickly. Basically the PS4 and XBone were hand crafted by third parties, and what did we get? Two near identical consoles so that porting is as easy as possible. They were almost able to get DRM in as well (which I think still might happen once these consoles reach a high enough install base).
Nintendo on the other hand? No, they'd have to actually do a LITTLE bit of work to make their games work on the system which is way too much for third parties. Why are they going to actually put work in to this system when the two other companies do whatever they tell them to? If anything, major third parties want to see Nintendo taken out. Nintendo can try to sway and woo third parties all they want, but just look at the current third party support and you will see the results. Every single game is intentionally and severely gimped in terms of content. Modes that are in every other version are taken out or their not giving it dlc. Why? So that third parties can have an excuse as to why they don't support Nintendo. At the end of the day, Nintendo can't force third parties to support them.
What makes it even worse is that when Nintendo occasionally does get an awesome third party exclusive, gamers either whine and cry or they just shrug off the game entirely. Even if GTA was on the Wii U and equal to all the other versions, gamers would still avoid it like the plague and instead get it on another system. At this point Nintendo's best bet is to simply expand their exclusive offerings and carve out a niche for themselves and make their profit while the HD twins continue to try to one up the other.
Exactly right, and also why the indie devs are being treated so well on Wii U so far. Nintendo wants people who are excited to bring games to Wii U, not a pile of arse put together in a couple of months like some of the rubbish from these 3rd parties.
These indie devs will bring great fresh content that will really help in between the Nintendo games.