Daggerfall is remembered and cherished so fondly by some gamers (including myself) because the sheer... EMPTINESS of it left ample room for our imagination to cultivate. Just like the Pen-and-paper RPG the series evolved from, the game gives you so little feedback as to the world around you that it was always possible (even encouraged) to make up your own story as you went along. Y'know, kinda like a "Role-Playing Game". To most people who haven't grew up with the series this quality imparts the game with a kind of sterility or dullness - mostly due to the hideously large dungeons and wasteland landscape - but to me the immense amount of patience and attention the dungeons required made even the most trivial "kill this werewolf" quest more substantial, as if each quest was a massive undertaking that my character will no doubt end up risking life and limb to accomplish. As my character grows in abilities, I become more comfortable in his skin, and with the game's seemingly large holes where actual content should be, I take the liberty to fill in the blanks myself and abstract them, gauging my character's reactions and desires along the way. Roleplaying.
As the series progressed, more and more of these blanks were filled for you and the experience became more akin to that of a fantasy-themed "amusemant park" where you're free to explore whatever you want, but within the confines of various predetermined setpieces. Lord knows the majority of Skyrim's quests railroaded your character all the way through, with the result almost invariably being you hacking your way through a linear cave or barrow with a locked or barred door near the entrance that you conveniently return to after beating the big bad Level-appropriate Draugr Murderdeathlord, reading the Word Wall, and getting dat phat loot from the big chest.
Now, I'm not hating on Skyrim or anything - I've garnered a fair amount of enjoyment from the game, mostly because they made combat so damn visceral and satisfying that its an engaging experience in its own right, but I daresay it becomes extremely predictable at times. This isn't helped by the pretty, detailed graphics which tend to make the "sameness" of the dungeons more pronounced than even Daggerfall's, in my opinion.
People who enjoyed Daggerfall will likely also enjoy this little game called Dwarf Fortress. Much like DF, DF (heh) gives the player nothing but the most archaic feedback about the world around him (in the form of ASCII symbols) and the basic idea of the game is that the more you invest your imagination in these little ASCII dwarf dudes and keeping them alive, the more fun the overall experience will be. And that's essentially all it boils down to when it comes to RPGs in general.