This was Nintendo's lineup of big games for all of 2015

1st Half

(3DS) Majora's Mask 3D - February 13, 2015

(3DS) Monster Hunter 4 Ultimate - February 13, 2015

(Wii U) Kirby and the Rainbow Curse - February 20, 2015

(Wii U) Mario Party 10 - March 12, 2015

(3DS) Codename Steam - March 13, 2015

(New 3DS) Xenoblade 3D - April 10, 2015

(3DS) Puzzles and Dragons Z + Super Mario - April 29, 2015

(Wii U) Splatoon - May 29, 2015

2nd Half

(Wii U)Fast Racing Neo - 2015

(3DS)Animal Crossing: Happy Home Designer - 2015

(3DS)The Legend of Zelda: Triforce Heroes - Fall 2015

(Wii U)Fatal Frame: Maiden of Black Water - Fall 2015

(Wii U)Devil's Third - August 4, 2015

(Wii U)Super Mario Maker - September 11, 2015

(Wii U)Mighty No 9 - September 15, 2015

(Wii U)Yoshi's Woolly World - October 16, 2015

(Wii U)Xenoblade X - December 4, 2015

(3DS)Yokai Watch - Holiday 2015

(Wii U)Star Fox Zero - Holiday 2015

(Wii U)Mario Tennis: Ultra Smash - Holiday 2015

In my opinion, 2nd half is much better (Mario Maker, Yoshi, Xenoblade, Star Fox, Fatal Frame)

What say you?

Forgot devil's third...

Added, thanks for the reminder

Just like in 2014, you sell more games in holiday than in May.

What about Xenoblade Chronicles 3D & PDZ+Super Mario Edition?

Also missed Mario and Sonic at the Rio Olympics. For both platforms. The Amiibo party game is also launching, but it's free so not a retail.

Also, while not a retail game, FAST Racing Neo warrants mention for Wii U.

Splatoon vs. Super Mario Maker.
That's hard.

I'll pick the 2nd Half because of Xenoblade

The Wiki says Mario & Sonic releases in 2016 

http://www.mariowiki.com/Mario_%26_Sonic_at_the_Rio_2016_Olympic_Games_(Wii_U)

Mario and sonic hits in Japan this holiday season so I think it'll reach in america around the same time as well.

First half for me solely because of Splatoon

as for Xenoblade X, Star Fox and Mario Maker, I'd consider getting them, but probably not day 1