That's kind of what I meant by "the variety of the environments and the fantastical nature of the content." Walking from a snow-capped mountain to a barren desert and then through thick forests would be suitable in Zelda... not so much in Skyrim. The difference is primarily in the audiovisual aesthetic: the sights and sounds of the world. As far as the actual gameplay function is concerned, Skyrim is very close to the ideal Zelda overworld. Just imagine if you took an Elder Scrolls game and "toonified" it, so that things looked more like these: It isn't when you look at the recent direction of the series. As the Zelda team has focused more and more on puzzles and gameplay gimmicks, the world itself has been stripped of meaning, eventually culminating in the disaster that was SS Hyrule.