Xenoblade Chronicles for its memorable cast, gorgeous landscapes, pensive dialogue, and ingenious plot twists. This game consummated everything that I wanted from an ambitious open-world adventure, and I still have yet to play anything that comes close, especially from a story perspective. While the side content is rather tedious (go kill X enemies, go collect X items, etc.), the pseudo-linear sense of progression encourages the discovery of hidden areas and secrets as the map fills itself out.
Xenoblade Chronicles X for its unbound exploration (after the prologue), insane emphasis on character customization, and the all-encompassing theme of survival as humanity works together. No video game world is as seamless as Planet Mira, and not even the original's Bionis/Mechonis duo can compare to the sheer amount of content hidden in the alien vistas. Despite being on the underpowered black sheep of this generation, XCX looks amazing on the Wii U and runs exceptionally well. And what it lacks due to its episodic story-telling, it more than makes up for persevering players who wish to take in the whole experience.
Both games are an inversion to each other; one fleshes out story and characters while the other focuses on exploration and customization. But together they fulfill what most other games can't by trying to be too cinematic or hyper-realistic and instead give the player complete freedom to decide their own course of action.