» Fri Nov 09, 2012 9:53 am
Because Skyrim's data system is actually very compact. The actual "data", that is quests, characters, locations, objects etc (NOT including the physical resources like meshes of course) is only 243MB in size. It's the voice files, meshes, textures and sounds that eat up space, but even then the BSA archives are really well compressed.
The GTA series is a lot bigger map size wise because it's more generic. The cars are generic, and apart from a few select people with select, specific cutscenes, people are just generic clones that react when you hit them. Apart from quest progress, there's nothing really that changes in the world. Plus, real life cities are a lot easier to plan than fantasy worlds, being much more grid like and regimented.