This is a tough one to answer...
BOTW comes to mind first. Just such a unique experience, especially at it's launch, but unfortunately the magic is predicated on the joy of discovery and breaking over the horizon for the first time.
If it were possible to capture the nostalgic imagination from years past, yeah it gets more open ended. Metal Gear Solid on PSX, first-gen Pokemon games, Baldur's Gate...it's funny how big and expressive those worlds felt, even though now I can basically see the entire tileset in my head/on the 'net somewhere. Still, there were some big feels and great things done for gaming with titles likes these, so, ya know.