So much this. I look at the current situation and... it's not the games that are the problem-- they're awesome. They're just not enough of a draw to justify most consumers buying a second system from the one they plan to use the most.
My kids and I play the s**t out of our Wii U, because of kid-friendly (and just really good) games like DKC TF, NSMB Wii U + Luigi, etc. If Nintendo would just swallow their pride and release their top games for other consoles as well they'd make a mint. Capitalize on whomever is the market leader.
I love my PS4, but the library is sorely lacking when it comes to kid-friendly or Nintendo titles. Mario, Mario Kart 8, Smash on PS4 would sell millions, and would actually be able to have proper online. It would give premier Nintendo franchises that much more exposure. Not to mention if they went with Sony it would give Japan a nice boost and of course PS4 an additional advantage versus Xbox. A lot of people would go PS vs Xbone if they knew they would get a few top Nintendo franchises on PS4, but a lot of those same people aren't going to buy a Wii U just to play Nintendo games (and certainly not at $300).
I think Nintendo massively underestimates the impact and profitability they would have if they brought their content to other platforms. Understood that they think they'll never be able to sell home consoles again if they bring their stuff to Playstation or Xbox, but isn't that sort of where they are at this point already?
I really think an 'our platform + 1' strategy for Nintendo's non-handheld offerings could be great, and would certainly help get them through these dark times.