For me personally, it's so freaking close between Persona 5 and Breath of the Wild.
Breath of the Wild is what The Legend of Zelda should be. It's the best Zelda game I have ever played (which is saying A LOT for the Zelda franchise!) and is deserving of every bit of acclaim and success it is receiving. It is the new standard of a historic franchise in my view. A franchise which includes my NOW 2nd favorite game of all-time, because my NEW #1....
Persona 5.... is so fucking awesome. I love this game so damn much. I just started my New Game+ play through. Now, during my 2nd play through is when I tend to be a little more critical towards a game, now that the first initial playground th is over and I know what to expect. And while there are a few nit picks here and there, it's still overall incredible. This title, I think, is the one that will break Persona through that glass ceiling to ascend to a higher level of popularity and prestige. It's one of those games for me where as soon as I pick it up, I can't put it down for hours.
Haven't played Horizon yet. I'm sure Red Dead 2 will live up to expectations. I have complete and total faith in Mario as well.
It may be liable to change but if I had to pick now, I'd say Zelda by a hair.