While I would love exploring and discovering those unmarked locations, I would then also require dozens of person map markers to mark them so I could find them again later.
Now, I could support unADVERTISED locations that never appeared on any sort of compass but were added to your map only when you actually discovered them. That would be pretty cool - see if you could discover every waterfall in Skyrim, or find "Ancient Tree" that serves no real purpose other than a random local landmark.
That sort of exploration/discovery is the major reason I play these games. (My problem is just that I play sporadically, so I'd love to be able to look at the map later and say "Oh yeah, Ancient Tree! That was neat, I should go back and take a screenshot!")
This exactly. I like to know where small structures are, especially if they contained loot. I don't mind having to find them myself, but for the love of God, if I as a player am interested in the location, I know my character would be. Put it on the map, please. It doesn't have to be advertised with a flashing neon sign. In fact, I kind of got insulted by the number of pinpoint quest markers in the game instead of encouragement to use my brain. So no, it doesn't need to be marked with a gigantic billboard, but I do want them denoted on the map once I find them myself.
It's not that Oblivion didn't have them... It's that they didn't show up on the map, and if someone forgot they were there it appeared to be rather barren.
By the way, the tall foliage and the steep inclines of Oblivion made exploration tedious. My character would constantly run into "I can't see more than 20 feet in any direction" or "slopes that it's impossible to climb" if I was on foot.
It was so difficult to get around on foot in many cases that ultimately it became easier to simply fast travel and ignore the "personal" exploration.