The Replicated Man/Android quest was actually one of the fondest memory I have of Fallout 3. At least on my first playthrough it was.
It was surprising for me when I first played this quest that, unlike the other quests I had activated, this one actually had no map markers in guiding you where to go or what to do, how exciting! Exploration was required!
And indeed, you could activate this quest in a multitude of locations through the tape recordings left near various clinics and houses, even all the way out at Paradise Falls. The idea that you had to find this one single character in the entirety of the map was a rather engaging idea. Further accentuated when a npc would come and track you down once you made a couple of enquiries regarding the android, and this npc would appear at random places, regardless of where you are located on the map. Further giving the illusion that this quest has a scale to reach the whole Capital Wasteland, and still not one single map marker!
Finally though, you'll reach through the quest's conclusion as you follow the main quest, leading you to Rivet City, and eventually given the last defining clue ... and you find out the man you've been looking for was the first person you ever got to talk to when you arrived at Rivet City to begin with! How ironic!
Of course in subsequent playthroughs it was hard to replicate (pun unintended) the engaging approach of the quest, especially since the game doesn't change the identity of the android at random for every playthrough, you can always skip straight to finale.
But that first experience was still there in my memories.
Meanwhile I would consider my least favorite quests of Fallout 3 to be the ones that always had the identical beginning and conclusions, along with no different method of engagement in reaching its conclusion: such as the second half of the main quest, all the fetch quests such as the nuka cola collection, the stradivarius violin, the slaver's collection list, and the majority of Point Lookout's side quest and main quest, as well as the unfortunately uninspired and short side quests of Broken Steel, all three of them, especially compared to the main game's side quest diversity.
The rest of the quests generally yields at least different types of rewards and unique items depending on your method of approach, so it at least warranted a worthwhile multiple replays.
At this point however after having done all possible variations and seen all possible outcomes, I have to agree that it is indeed a shame most of the quests have an air of 'triviality' to it, and now as I replay through the game it becomes more of a checklist of "which reward do I wish to gain this time around" rather than the initial first time experience where every outcome initially seemed as rewarding as the other.
Oh well, better luck next time. Hopefully.
. The reasoning behind the story was also terrible. I liked The Legend of the Star in New Vegas, though, because it parodied fetch-quests.