Oh yeah, I totally forgot about HW! That'll definitely be the next one. 

Hyrule Warriors most likely. If not that then Zelda.

game would have done much better if not exclusive to gamestop

Zelda.

Could be Hyrule Warriors, Mario Party, or Splatoon

I'm going to go with Mario Party

this one will sell better. The series has gotten a lot more exposure to people recently , an example being smash making it more popular to the mainstream.

Also had a very limited release.

let me give you the rundown.

1. kirby games have rarely sold less than a million. ever. this is at a budget price (39.99) and seeing the wonders that has done for toad, rainbow curse will reach one million by the end of the year almost without doubt (as will captain toad, which is already at 430k and likely more, around 500k, with all the figures from europe). look it up. kirby sells no matter what. even shitty kirby games like kirby air ride? yup. 1m+. and this will be a good one.

2. no mario party has ever sold less than 1m. EVER. not on gamecube, not on n64 (obviously), not on wii. ever. (mario party advance is undertracked here, nintendo confirmed 1m+ sold). if you think this won't sell, especially with the amiibo focus ("amiibo party") and a whole line of amiibo built around it... well...

3. splatoon is an unknown quantity, but the hype for this game is real. we'll see.

4. yoshi games sell, see point #1. kirby's epic yarn was a fan favorite, this is a sequel from a beloved developer whose games for nintendo have never sold less than 1m. again, ever.

5. mario maker's closest point of comparison is mario paint. if they distribute this intelligently (digital and physical, but really pushing digital and the online connectivity and sharing aspect with a set of pre-created levels) and price it at 39.99 or 49.99, it will sell like hotcakes.

6. this is very perceptive of you, but xenoblade chronicles sold 800k+ while being available only at gamestop. now it will receive a wide release. the people who bought it on wii were the hardest of the "hard core," and those are the same people who bought a wii u right away. this game will do 1m, especially after the reviews it's going to get.

7. zelda will sell a million in the first week, not the first two. pre-orders for zelda games are routinely 500k+, even for relatively low-selling installments (skyward sword, for example). this is a completely new direction for the series. it'll do at least as well as 3d world, probably a little better.

ot: hyrule warriors by march, that game is steamrolling to 1m. lego city undercover will eventually, but sales will slow with the holidays over. pikmin 3 will too, once supply issues are resolved. these last two have already already sold 1m+ retail+digital, tho. reggie says digital sales are usually between 10%-20% of sales. assuming just 11%, both are at 1m.

Splatoon looks sick as hell with the hub, customization, etc. so I think it attracted a lot of new players. I pick splatoon.

After Donkey Kong, Hyrule Warriors, because Pikmin is most likely at 1 million with digital... Idk about Lego.

And from the new releases, I say Mario Party 10 will most likely reach that milestone first, followed (hopefully) by Splatoon and Mario Maker. Xenoblade and Zelda will reach million for sure. And then Bayonetta 2 by 2016

I will go with Mario Maker, this game has potential.