As much as I hate to say it, they need the sports titles and generic annual shooters. Beyond that, they should focus on getting a few exclusives from Japanese devs.

They definitely need EA, Activision, Rockstar and Ubisoft's support. In Japan they don't struggle, so Japanese publishers aren't as big as a priority as Western ones are.

THIS.

But it won't happen... T_T

They need to get as many developers as they can on board. They were doing this with the Wii U with EA, Ubisoft, Activision, WB, Capcom, etc., and they shouldn't stop there. They should go after developers that they historically haven't had a big relationship with like Bethesda, Epic Games, Blizzard, etc. 

Nintendo also needs to, as much as I don't want to say this, compete. They need to secure timed exclusive DLC, marketing, and all that jazz. The problem is they don't have as much money as the others to do these things as we saw in the Gamecube era. If they try to wage a content war with Sony/MS they will get their butts kicked, but it's something they need to do to be successful.  

Someone quote me and answer this: What should NIntendo do at this point? They don't really have the money to "compete", they're betting the farm if they try to catch lightning in a bottle again, and if they screw up then it could spell doom

Idealy, as many as they can get. The best ones would be the big names, like the western games. Personally, I'd like more Japanese 3rd parties on the NX. I love me some JRPGs and Japanese games in general : )

Because I feel that it would get reduced to a handheld franchise(it kind of already is)

GTA, CoD, Bethesda games would be the big 3. Anything after that is bonus. If they can get these deals then they should be set for the big games. I like the Japanese deals that Nintendo gets but its not that big in the west. At the very least, getting those 3 will keep them viable for the average consumer. Plus adding the annual sports franchises would be huge for them.

They should stay in Japan: Yakuza, Resident Evil, Silent Hill, Metal Gear, Final Fantasy, Castelvania, Ridge Racer, Tales of, Tekken, Dead Rising, Devil's Fourth, Kingdom Hearts, Sonic, Ninja Gaiden, No More Heros, Bayonetta and a lot of others.

In Japan: mainly keep Monster Hunter and Yokai Watch. And some Dragon Quest

West: Fifa, GTA, CoD, Elder Scrolls...

I also really think they should have a western blockbuster franchise of their own. Maybe their own fantasy RPG, or action game like Uncharted/Tomb Raider.

I noticed that they have been doing a lot of stuff with Capcom especially with Monster Hunter and I even think some of Capcom's IPs are ending up in Smash bros, so I expect Capcom will be working with them on the NX.