My 2c
The Realms feel like a living world to me. It's so full of history, detail and lore to discover (and intrigues/mysteries left hidden within that lore), that it's like visiting a world that has seen eras being shaped by people and icons, each region with its own history and flavor. Not only that, but the richness in details about people and factions pursuing their own goals makes the world feel alive, as if it kept ticking even when you're not watching or playing in it. There are also some characters or gods or nations that I really, *really* like, so they contribute to my fondness of the setting too; but the general reason is that which I have described. While other settings can feel alive too, none of the D&D settings can provide that kind of feeling, as far as I've seen. In short, the iconic part of the Realms is how deep the characterization of the world and its history goes.
The Realms feel like a living world to me. It's so full of history, detail and lore to discover (and intrigues/mysteries left hidden within that lore), that it's like visiting a world that has seen eras being shaped by people and icons, each region with its own history and flavor. Not only that, but the richness in details about people and factions pursuing their own goals makes the world feel alive, as if it kept ticking even when you're not watching or playing in it. There are also some characters or gods or nations that I really, *really* like, so they contribute to my fondness of the setting too; but the general reason is that which I have described. While other settings can feel alive too, none of the D&D settings can provide that kind of feeling, as far as I've seen. In short, the iconic part of the Realms is how deep the characterization of the world and its history goes.