Unpopular opinion here.
I love the BGS games (Skyrim, Oblivion, FO3, hell even the much-maligned FO4) not for the main stories. Or the characters. Or the gameplay. And, dear god, not for the performance or quality of them.
It's the DETAIL. There's just so much freaking stuff to discover, and none of it is forced upon you.
I'll give some examples: In Skyrim, I stumble into blackreach, this freaking enormous, beautiful underground cavern. I run into the remains of a long-dead expedition down there, among many other interesting bits of lore.
In FO4, I enter a random building. No quest, no one told me to go there, just looked interesting. A mister handy wants to hire me for a position in a science lab... OK. So I go in, get trapped like a lab rat of course, and discover this long string of lore about these poor bastards who were trapped in a science sweatshop by a manager as the world outside burned in atomic fire. I walk into another building, learn that a deathly boring logistics robot I ran into earlier was actually a prototype AI haphazardly transplanted into an Assaultron that advised the president during the not-so-cold war, among other things.
And, dear god, the Shivering Isles in Oblivion... it's been a long time, but every single settlement was chock full of mental writing from the insane residents.
See, the TES games are primarily exploration games to me. The gameplay is just filler, and (with a few exceptions) quests are just convenient directions to interesting places filled with lore and stories to read through, as well as beautiful sights and sounds to take in. And, unlike other games, the wide-open nature lets you skip the stuff you'd rather not read and move to something else.
Now, I'm probably in the minority. 99% of Skyrim players aren't gonna pick up and read a book unless it has a quest marker on it.