It kind of depends on what kind of gamer you are if "long lasting appeal" if what you're looking for. The obvious answers are MK8 or Smash 4, as they'll last a generation, but they have the same caveat that all multiplayer games face. Once you've raced every track or fought every character, everything you do becomes repetitive, and your enjoyment comes more from who you play than what you play. If you're looking for something to play alone, these are poor choices unless you love the games enough to constantly play online. I do, but as someone without the history, you'll need that multiplayer experience for everything to click.
If you're like me, SM3DW is the best answer, but it also comes with a caveat. If you're the type of person who will finish the game in one sitting, it's not for you in terms of longevity. I got the game at launch, and I still haven't finished it. That's not because it's bad, but because it's nicely designed to be consumable in chunks. I never play more than a few levels at a time before I move onto something else. It's a good "appetizer/time waster" game. It's popcorn. It's like a snack in game form. And it's excellent at doing that. The problem is that it's also very, very well designed, which means that you might think it's so good that you do finish it in just 15 hours because you decided to marathon it.
If you're like me, that won't be an issue, though. There isn't really anything else on the Wii U that fits your description, though. No matter what anyone tries to say, there are gaping holes in the Wii U's library, and the biggest one is a strong single player game one can sink hours upon hours into without feeling like you're wasting time. There's just no game like it on the system yet other than remakes. Xenoblade sounds like the first one. Maybe Splatoon can do it if it's single player campaign is good enough.







