There were plenty of exclusive Wii games that were definitely good reasons to own a Wii, despite it being an under-performing system. While you personally stick with the conventional franchise titles, remind yourself that there were many gems on the system that were either overlooked or people never bothered looking into, similar to the GameCube and N64 libraries as well. With games like MadWorld, The Last Story, Xenoblade Chronicles, Arc Rise Fantasia, The Conduit, Deadspace: Extraction and a plethora of other third party gems that people just overlooked completely (or ignored for various reasons), the selection of Wii games were still pretty robust, even when compared to the previous consoles.
Also, you can play your Wii games on the Wii U if you're not satisfied with the console either.
As for the overall hardware for Nintendo, you'll have to look beyond the first party library for both consoles they clearly have more than just Mario and Zelda.
What it boils down to for me is how much the Wii sucks, and there's nothing that will make it not suck for me. I'm not at all impressed with what I think is a weak setup. I still haven't finished Skyward Sword yet, because I don't enjoy playing on the Wii. The game selection also sucks.
If it wasn't for the popularity of the Zelda and Mario games, Nintendo wouldn't have much of anything going for them these days.
There are no plans currently for another Metroid game since the original trilogy is complete. Plus, Retro Studios, the people behind that trilogy is working on the Donkey Kong Country Returns series, and likely making another one for the the Wii U. Regarding new developments, Nintendo is working on a Star Fox game, which debuted (in passing) alongside the new Zelda game that's coming out. But, despite it being slated to come out this year, it seems less likely.
Yeah, there's a multitude of Zelda fans out there, but that's the case with so many of Nintendo's various series/characters from back in the day. It would be awesome if they'd bring more of my past faves to the current systems.
Hmm...I've heard that there are plans for Metroid on the Wii U & the 3DS in the works. Hopefully you'll get what you're hoping for.
