I can amend this and say definitely Zelda. I'm going around, doing side-quests and stuff. There are so many things to do, many smart things to find. This is the first open world game that I've truly wanted to explore. I love the fact that this game is huge, vast and vertical. The draw distance is the most impressive thing to me about this Zelda. If you are high enough in some areas, you can see clear across the entire map. That is amazing.
The thing about Zelda is the way things work....actually make sense. Like if you think of something, with the tools you have it makes sense that it works, but its still like "Wow I can't believe that actually worked" because so few games actually let you be creative in such a way.
There are plenty of open world sandbox games, but in zelda everything works like you think it would in your brain.
The world fits together and flows together like you think environments and worlds would and should.
One of the 1st thing I did when I started playing horzion after zelda was try to climb up a hill because it was inbetween the shortest distance for two points.... and got to the wall jump and was like "oh yeah, it does work like that..."
Going from hills, to bushes, to water to a cliff feel smooth and effortless in zelda, something other open world games have yet to really get right...