Frankly, I can't see how people can call "exploration" the act of following passively a quest mark on a compass/minimap.
What you call true open world I call boring wandering around, and no, open world games with static mobs aren't false open-world. A) Because at any given level they give you many places/areas to visit b) Because usually they feature not-so-obvious ways to explore high level areas before you have the suggested level for doing that.
As for the replayability, I don't think a game where you can max all the skills, become master of all the guilds and finish (almost) all the quests in a single playthrough is designed for replayability. You need consequences to have replayability, ad TES games have VERY few of them.
Again: I'm REALLY glad that Original Sin has nothing in common with the latest TES game.
The quest system is one of the major reasons why I consider FO3 and Skyrim to be flawed: they also undermine exploration. If you ignore them, and even on subsequent play-throughs, it's a great feeling to be able to just go wherever you like (maybe an area that you never paid much attention to on previous play-throughs), instead of being forced to follow pretty much the same path every single fricking time.
