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".
Well, name is a difficult thing to assess. Would you really call the kid icarus: uprising a big title since it has a well known Nintendo ip on the cover. Would you call fallout shelter a big title since it has fallout on the cover? Does mario kart not count as a big game because it is a spin off?
point is, things aren't so simple as putting a known title on a game and calling it big. There are various circumstances that go into it.
The thing is, star fox really hasn't had a huge title in a very long title (the last one being a remake of the n64 version). Starfox zero having the title of starfox really doesn't tell much to the average customer that has probably only heard of star fox through super smash bros and the "do a barrel roll" phrase. On the other hand, titles like gta (that has broken records), or destiny (huge budget), or pokemon (a center point of many childhoods), can get sales through name alone, since they have broken more records than starfox has in the last decade.
The level of marketing for mario maker is just on a different level than starfox. Just look at how almost 1/3 of the last e3 was spent on mario maker. The marketing for mario maker will most probably make it a 'big' title on the scale of mario kart, but I don't see that happening whatsoever for starfox. And while it may seem like Nintendo is making a 'big deal' about starfox, I think it's more that they really don't have much else to make a 'big deal' about. Devils third is gone, fatal frame is niche and may just be digital in the US. This leaves the wii u with only 4 retail releases left this year and practically no third party.