You guys are comparing the big games from PS4 and XBO to those from Nintendo...
Nintendo games don't have much high resolution textures and other assets are usually kept to a minimum compared to games like GTA V, The Witcher 3, or Uncharted 4. They also don't make use of voice acting as much (if at all, in certain cases), so there aren't much lossless audio files in their games, nor do they make extensive use of pre-rendered videos.
It's not that Nintendo do magic with compression (seriously, guys... -__-). It's simply that they make games that don't require a lot of space to begin with.







