Wii U by far. barely touched it. Just Hyrule Warriors, Tropical Freeze, and The Wonderful 101.
Next is 3DS. Only played 6 games on it, though I own 12. I always felt something was off about it. It's the same basic shape as the DS Lite, but for some reason it never feels as good playing on it, so I always use my Lite instead of backwards compat on the 3DS. Never played an XL. On the whole, I'm glad it's almost done. I'm over these super low res 3D games.
Next is the Vita. Which is a shame cause I love the system, but it just didn't get the support. I only ended up playing through maybe 8 games on it. I do have a good number of PS4 games that have Vita versions though, so the practice of making the games available for console too contributes to me not touching it.
It sucks how sparse this gen's portables are, when I had a good 25 games on both the DS and PSP.