"Relationships" in videogames are pointless unless they actually improve the main narrative/story of the game (like in Mass Effect). And I don't imagine Bethesda's first rendition of "relationships" in a videogame will be all that great, and I especially don't expect it to enhance the narrative in any way, so the easy answer is none of the above.
My friend, I believe you are confusing your personal Skyrim narrative with some form of "definitive" Skyrim narrative.
Within the world of RPGs and Action RPGs, there have been some very well-done games by developers like Bioware that allow the player to experience an epic story that is fully fleshed out, where the PC has a predefined role to play with some choices that affect the final outcome.
And on the other hand, there are developers like Bethesda that immerse the player in a wide open sandbox narrative where you are at greater liberty to define the story's arc yourself, for example, who your character is, where he comes from, which NPCs he wants to befriend or flirt with, why he does what he does and which quests and organizations he wants to join.
Neither is necessarily better than the other from an empirical perspective, but on a subjective level, some RPG fans prefer one or the other, and some enjoy both types of games.
In your personal Skyrim narrative, certainly, NPC romance or relationship features might play the tiniest of roles, or even no role at all.
In my personal Skyrim narrative, these features could play an even larger role than Esbern and the Greybeards, for example.
To provide some background, I have been playing Oblivion for years and I still have absolutely no idea what happens after you take Martin to Cloud Ruler Temple. In fact, during my latest playthrough, which I started at the end of 2010, I have racked up over 300 hours, without even touching the main quest or setting foot inside any Oblivion gates yet.
My personal narrative for this particular playthrough is the tragic tale of a young, naive Dunmer orphan who defends herself from the advances of a corrupt palace guard captain in Skingrad and accidentally kills the man. After she falls in with a bloodthirsty cult of assassins, she begins plotting her revenge on all those who wear the hated red garb of the Skingrad city guard. Although she has begun to master the ways of stealth, archery and poison making, this Dunmer does not even know what an Oblivion gate looks like. In her narrative, the Dark Brotherhood and the Skingrad City Guard play a much larger role than the Blades, for example.