Xenoblade Chronicles X impacted me for life. Never before have I been so impressed in a game's visual design and sheer scale, mesmerized by its incredible music and immersed in its phenomenal world. It also made me discover the original Xenoblade (through XC 3D).
Star Fox Zero, despite its flaws, was a thoroughly enjoyable arcade romp for me. It's my favorite StarFox, and the gyro aiming is genius. Without the dual screen gimmick and with significantly better graphics, a good few more of the good levels (like Corneria) and fewer/none of the obviously filler ones, but keeping the world, visual style, music, vehicles (sans GyroWing) and gyro aiming, it could be one of the greatest rail shooters I've ever played.
I know that's a lot of caveats, but the core really is superb and it breaks my heart that it's most likely going to be dropped forever.
Mario Kart 8, Mario 3D World, NSMBU and Smash were all extremely good games on their own right, but also as someone who was a huge Nintendo fan but skipped the Wii, a very nostalgic return to Nintendo for me.
I also got to experience Bayonetta 2, which I don't think needs much explanation.
Finally, Off-TV. I still think that the Gamepad is powered by magic given that I cannot achieve its absolute rock solid stability wirelessly with PS4 RP or Steam Streaming no matter how much I spend in networking gear. The Off-TV use case has been a godsend for my lifestyle and it's the main reason I can't wait for the Switch.