Breath of the Wild for me so far. Haven't bought anything released in 2017 besides BOTW and KH1.5+2.5 HD Remix, which I'm not sure counts because its been released before on PS3, though as separate game collections.
I want to try Nier, Horizon, DQVIII, and Nioh later on and I cannot wait for Splatoon 2, Mario Odyssey, Mario Kart 8 Deluxe, Xenoblade 2, FE Echoes, and FE Warriors.