Yes, Nintendo's exclusives are primarily first party games. Yes, Nintendo has a lot of first party games and very little third party support. However, that doesn't negate the fact that their first party games are (for the most part) fantastic! The proof is right their in the Smash Bros. franchise: not only is the Smash Bros. series amazing, but the majority of the games which characters come from are as well. Hardly anyone who has played a Zelda game, a Metroid game, or a Mario game could claim that this are not good franchises. "Same old characters" isn't such a bad thing - at least Nintendo knows what they're good at.
Not to mention... The Wii U is backwards compatible, unlike Xbox One. (And information on backwards compatibility for PS4 is a bit fuzzy at the moment, if I'm not mistaken). I'm quite confident that the PS4 will demolish Xbox One on launch unless Microsoft changes some things dramatically, but I'm still holding out that the Wii U will emerge in a much better spot a couple years from now. Microsoft and Sony can duke it out head to head trying to win all that third party support, but Nintendo offers a unique experience that neither of the others do, and that's why I think they're greatly underestimated in the "console wars".