This thread is bad, and you should feel bad.

Every game, or every console is just filler till the next console.

Its a bit silly to say. I am still very curious about what the NX will be. I predict a surprise because Nintendo has never said that the NX would replace the 3DS or Wii U, but that it would be the third pillar. It will be funny to see the meltdowns.

Is there an actual agreed upon definition for what "filler" is in terms of video game releases? As opposed to smaller or more niche games?

:/
on one side I can see what you're trying to say and I kinda agree with you because I myself believe that the budget for the game wasn't even close to the one every main Mario game gets, on the other end it's really a clever choice since it's Mario's 30th anniversary, fans aren't complaining and as far as people keeps playing the game won't end...
I could very likeley see Super Mario Maker beeing re-released on the NX and I would highly suggest them to do so...

MP: Federation Force is the definition of Filler :v

In my opinion, filler is a small or not "so important" game to fill gaps between big games that are not planned way before release. For example, some big guns for Wii U are Yoshi Wolly World or Xenoblade X that were announced since January 2013. On the other hand, Amiibo Festival looks like something done in a few months and that is done to fill gaps between bigger releases. Just like Mario Tennis Ultra Smash.

I agree with the OP on calling Super Mario Maker a "filler" because that was the original plan. I mean, the game was supposed to be between releases like Yoshi, Star Fox, X and Zelda. And this is only a level editor.

In the end, this game got a lot of effort put in and became big, just like Splatoon, which I'm sure Nintendo never expected to be that big.

I think the apropiate definition of filler would be those titles released between big releases, releases bigger than it, to avoid droughts and keep the audience on the system. Since Mario Maker can be considered a big release on its own, I wouldn't call it filler. But it has nothing to do with quality, just with scope and ambition.

It might be but it is still a good filler. I have enjoyed watching people play it on twitch. I'm hoping that NX has BC.

I don't think Nintendo ever expected Yoshi's Wolly World to outsell Mario Maker so that would make YWW the small game of the two.

For you absolutely everything except your mainline AAA Zelda game is a filler.