Before I even begin, let me just go ahead and say this. Nintendo is NEVER going to convince anyone who didn't own and Wii or a DS or a 3DS to buy a Wii U. Ever. If you were a firm supporter of the PS3 or the Xbox 360 you've made up your mind on who to follow long ago and Nintendo's latest console isn't going to change anybody else's opinions. However, I think that Nintendo can have just as much success with the Wii U as they did the Wii and they only need a few things to do it.
1) Make it an Entertainment System
If Nintendo ever expects to gain back their casual crowd this is the first step they need to take. Similar to what Microsoft has done with the Xbox 360, they need more entertainment options. Microsoft has been smart with their system by opening it up to all sorts of entertainment applications. Not to say that Nintendo hasn't begun to do this however. Netflix, Hulu Plus, Amazon Instant Video and Youtube are all major applications and the inclusion of Nintendo TVii that connects not only these but everything on a person's cable box is impressive. They've taken a massive step forward. Yet, all four of their current streaming providers are also available on the Wii. Shouldn't the Wii U offer something different? HBO Go, Vudu, Flixter, Crackle, Cinema Now and even more should be coming to the Wii U. Get as many options as possible for consumers. Why stop there? Why not include music streaming like Pandora and iHeartRadio? Or even add applications for digital copies of movies and mp3 files of songs. All of these entertainment features will make the Wii U a relevant option for tons of people that currently don't even pay attention to it. Include the special second screen experience with all of these and it could prove to be a good reason to pick one up.
2) Apps, Apps and more Apps
Once again, lets take a step in the more casual direction. Since the release of the Wii and the DS people have slowly drifted towards mobile devices sporting iOS, Andriod, Windows or others. Remember back at E3 2011 when Nintendo showed people playing little board game type things using only the gamepad? What about the drawing application? Why not add tons of smaller games and applications like that? Nintendo are starting to move towards this with Unity and Nintendo Web Framework which is a good sign however not much has come out of it yet. Nintendo's own virtual console isn't even fully up on the eShop yet. Nintendo need lots of smaller iOS like games. The idea of being able to play these on your TV may be able to draw the casual market back to Nintendo. Add in the entertainment options and it would be the perfect casual machine for families' TVs. Fill the eShop with not only games but as many applications as possible. Currently there are things such as Google Maps, Panorama View, and UPlay but that's not enough. The more the better. Make the eShop as big as the App Store for Apple.
3) First Party Games
Luckily this is what Nintendo always knows what to do right. I can't think of very many times a first party Nintendo game has ever steered someone wrong. Entertainment and smaller applications may draw in the casual crowd, but nothing will draw in Nintendo fans like 3D Mario, Zelda, Mario Kart, Metroid, Pikmin, Smash Bros and more. Maybe even if we're lucky a brand new major IP could be announced for the Wii U at some point; a moment Nintendo fans have been waiting much too long for. Even better news is that almost all of these games are on track to come out within the next year. A good sign. Hopefully Nintendo can produce at E3 and get fans excited to play some great games.
If Nintendo hopes to be nearly as successful with the Wii U as they've been with their last batch of hardware than these three things (at least in my opinion) are vital. They could make or break Nintendo. Luckily, in the case of the last two, it looks like Nintendo is making steps towards them and should have lots to say come E3. I have complete faith in Nintendo to bring all of their fans to their console. What will be interesting to see is if they'll be able to realize what they need to do to recapture the casual crowd or if they can even go the step further, gain some serious third party support (outside Ubisoft, Warner Bros and SEGA) and get maybe even get a new group of hardcore gamers to make the switch to Nintendo, although that is definitely a stretch.