Wii U basically averages two "big" games a year.

[S.Peelman]

I'd still say Star Fox is a big release for WiiU. 'Name' goes a long way as far as I'm concerned and Nintendo gives the game substantial exposure. I'd say production values are secondary to kind of light the end product is represented by the publisher, in this case Nintendo. Or sales too, tertiary even, because that's after the fact. If a new GTA flops, you can't really say "Oh, it was just a small game afterall".

They are making 'a big deal' about Star Fox, so it's presented as a "big game" (I would preferably call those 'primary releases instead though) to the world and that's what counts most in my book. Mario Maker is similar, the game probably costs next to nothing and the development team probably doesn't exceed a dozen people including Tezuka and Miyamoto, but they clearly are bringing it with huge fanfare and are trying to create huge hype.

Now there's where I would disagree with OP, because a lot more games than just two are brought as being 'big games' every year. There has also been Donkey Kong, ZombiU, Bayonetta and Xenoblade and Yoshi soon for example. They've been getting plenty of 'screentime' to justify calling them 'big releases'.