Question 1: How did you feel about the quest guidance in Morrowind, having to use your journal for quests? How did it feel in terms of immersion? How did the quest guidance system in Morrowind affect the difficulty of the game?
Those questions depend entirely on whether we're talking about vanilla Morrowind or the updated journal from the expansion. If it's vanilla, then the quest guidance in Morrowind is terrible. I'd have to look through seemingly-hundreds of pages of my journal--mostly about rumors--just to find a paragraph about a quest. It wasn't very immersive, because I didn't actually write those paragraphs, and it was just annoying. It affected difficulty slightly, but only in the sense that it made it difficult for me to do what I wanted to do.
If we're talking about expansion-updated journal, then it was much, much better. Still no more immersive than vanilla, but it made things much easier while still requiring me to pay attention to what I was doing.
Question 2: How did you feel about the quest guidance in Oblivion, having quest markers for most quests? How did it feel in terms of immersion?
Better and worse. On one hand, I never got lost like I did in Morrowind. On the other, I didn't have to pay as much attention as I did in Morrowind. I'd say immersion definitely takes a hit when using quest markers.
Question 3: What kind of quest guidance system should be implemented in Skyrim? Should Skyrim have both systems for all quests, the option to turn quest markers off? Why or why not?
I'd want a journal that categorizes quests, ala expansion-journal Morrowind, as well as the option to turn quest markers on or off at will. They've also implemented a "Clairvoyance" spell (or dragon shout?) that will guide the player to his/her objective in an immersive, lore-friendly way, while still being totally optional. Very brilliant.
Question 4: Have you ever played Two Worlds 2? How did you feel about the quest markers in that game?
Nope.