World building is much more than only placing the right building in the right place. Don't focus only on that. Again, look at the way each area is designed, without taking into account what other areas are next to it.
It's also much more than deciding what area's are where...
World building generally relates to building a real world, all aspects of it, and whether it feels real, and alive. Just building placement, or even area design, does not make that. I only used the building's as an example so I didn't have to go into excruciating detail. The outsides of buildings may be detailed, but they don't bother to do internal design unless there's a reason, gameplay wise, for them to do so. Outside of missions, the NPCs you come across are mostly random agents who spout random lines, they have no depth and do not grow. The NPCs you can talk to properly, are generally there to start an activity or a mission. The closest GTA gets to it is the phone, the fact you can phone people up makes it feel a bit more realistic, but that's about it, and even Shenmue did that, 15 years ago.
I dunno, all of those add up for me, and consequently, I don't feel the world is alive at all. It just feels like the world is there solely for the game play. That's isn't necessarily a bad thing for the kind of game Grand Theft Auto is, of course.
World design is another kettle of fish, and yes, Rockstar do a fantastic job of building an amazing representation of LA. In terms of design alone, Rockstar are pretty un-matched.