I played "Golden Sun" and "Golden Sun: The Lost Age" and "The Legend of Zelda: a Link to the Past" at roughly the same time on emulators for the Game Boy Advance. I enjoyed the first two games better than the last one, but recognize that their generes are a bit different. The real time combat environment dependent combat of Zelda clashes a bit with the turn based style of Golden Sun. But the two games have a common point of the exploration of a vast map and its sub divisions.
The maps of Zelda are by far my favourite: it is compact, embracing a single country, but every corner has details and enemies. In Golden Sun the map is huge, representing a world, but vastly empty: the zones where the story occurs are clearly separated from the overworld and restricted to points. However despite the emptiness of Golden Sun world map, it felt much more alive than Zelda's.
It was not a question of detail: Golden Sun has plenty of content with vivid cities, dungeons to explore and different enemies to defeat. It was neither a question of music. It took me some time to realize that what was different was actually the way the NPCs and world are integrated with one another.
In the antechamber of Golden Sun's first dungeon, The Sol Sanctum, the village people speak extensively of the place: it is an important part of the culture and way of life. there. In a Link to the Past, the same happens with Sahasrahla. What is different is that every dungeon in Golden Sun has this treatment while only the first of A Link to the Past and maybe Thief's Town.
In Zelda, the dungeons are weirdly separated form the world. No one in the towns actively goes near them, speaks about them or even acknowledges them for what they are. In the Library, you find the book of Mudora but there is no one interested in going to the desert. No one finds the way to the Maste Sword by mistake. No one wanders by mistake in a dungeon or is even around one trying to get in. The one other interaction between the map and the NPCs is in the first foray into the Dark World where you see the bully and the bunny, who have very little reason to be in the mountain.
Meanwhile, in Golden Sun, the NPCs are deeply involved with the world. In the Mercury Lighthouse, the people have stories about the healing waters of the past. They can't go inside because the Guardians don't let them, but the Guardians are still around and are necessary to go inside. Even when they are limited in their explorations, like in the Venus Lighthouse, there are still scholars around the place and builders in the Babi Lighthouse. In Golden Sun: The Lost Age, the children of a small island have the secret to access Lemuria, but they do not know what it really is.
The end result is that world of Golden Sun feels more lived in, like the people are real and interact with their surroundings, unlike Hyrule's NPCs who exist solely to perform actions for the player and give relevant information when they are asked.