Kagome by far.
To explain why, let’s first look at Inuyasha and Kikyo’s relationship before Kikyo’s death. Contrary to popular fandom belief (as well as to what the anime would have you think), it wasn’t exactly a deep and loving romance.
On one hand, you have Inuyasha, fighting for his very life from a very young age. Ever since his mother’s death, and possibly even before that, he’s constantly been told that he’s not worth crap and ostracized by pretty much every other being he comes into contact with. Humans hate and/or fear him because he’s half youkai, and youkai think he’s weak or worthless because he’s half human. Living under those circumstances for around 7-10 years (depending on how old he was at his mother’s death, presumably 5-8) leads to a crap ton of heavy mental barriers. He can’t show weakness. He can’t trust anyone. It’s kill or be killed. There’s no place for him, so he has to make one for himself. But this place he’s made for himself is incredibly lonely, as he’s the only one in it. If he can’t have a place, he might as well at least have power. So he begins to seek the Shikon Jewel so that he can become a full youkai.
On the other hand, there’s Kikyo, local priestess of a small village tasked with the duty of protecting the Jewel. Over the years of preforming this duty, she becomes fairly closed-off emotionally. Like Inuyasha, she “can’t show weakness”, else the youkai will take advantage of that and attack her. She feels detached from normality. Though she continues her work, she wishes to be rid of the jewel and live as an ordinary woman.
Then the two meet. Kikyo takes pity on Inuyasha, in whom she sees a bit of herself, and though the thwarts his attempts to get the Jewel many times, she never kills or even wounds him. This behavior intrigues Inuyasha, and they talk a few times.
Kikyo begins to think that, perhaps, if she uses the Jewel to make Inuyasha human, perhaps it’ll be “purified” because it was used for “good” and disappear, thus freeing her of her duties. Would this plan actually work? Probably not, as we later learn that there is only one wish that will destroy the Jewel, which is literally wishing for the Jewel to disappear. However, Kikyo was desperate. She wanted to be rid of her duties and just be normal. It’s also important to note her perspective here: that “purifying” Inuyasha of his youkai side was an act of kindness. In other words, she didn’t love him for who he was. She only loved his human side, or in other words, she loved the idea of him, not necessarily him, himself. She wasn’t acting as much out of concern for him as for herself.
And Inuyasha? For the first time since his mother’s death, he’s being offered a place. Sure, it’s not what he’d been imagining, but it was something, and it was right there in front of him. So, in what he later admits to be a rather spur-of-the-moment decision, he agrees to Kikyo’s plan, not so much for her, but for himself, anything to end this life of loneliness and cruelty he’s been forced to live for so long. Once again, he’s a bit more interested in the idea of her than in her, herself.
Then Naraku steps in with his false betrayal trap. What’s interesting to note is that neither Inuyasha nor Kikyo doubt for a moment that it really was the other attacking. There’s not so much a “this can’t be; I trusted you!” moment as a “well, I knew it was too good to be true” moment.
And therein lies the problem with their relationship. Neither of them really fully trusted the other. Very earlier on, in chapter 40, Inuyasha blatantly declares that he doesn’t trust anyone. He again asserts at the end of the series that, until meeting Kagome, he didn’t know how to trust. THIS INCLUDES BEING UNABLE TO TRUST KIKYO.
So here comes Naraku, destroys Inuyasha and Kikyo’s “relationship”, makes them hate each other, etc., etc., you know the story. Kikyo dies and Inuyasha is sealed to the tree.
Kagome grew up in the modern era not believing in youkai and thus without the bias against them. When she meets Inuyasha (after the centipede business is taken care of), she doesn’t treat him like a lesser or a hanyou. She very clearly and openly treats him like just another person. She doesn’t see his white hair, claws, and dog ears as markers of an abomination, but just as characteristics of him. She pretty much accepts him as he is without a second thought.
Of course, this throws Inuyasha, who now bears not only the scars of his rough upbringing, but also of the “betrayal” of Kikyo, for quite a loop. At first, he throws up his barriers around his heart. If there’s anything he’s learned from what he’s been through, it’s that opening up to people only makes you vulnerable. He doesn’t want to risk another Kikyo situation.
But slowly, over time, Kagome begins to melt these barriers. Even the resurrected Kikyo comments to Kaede on the change Kagome has invoked in Inuyasha in just 78 chapters, and I quote:
"His expression has become much kinder. Back then, that guy looked like he didn’t trust anyone…he had a peevish expression. That girl, Kagome…has changed Inuyasha?"
Going along with this, let’s not forget that this book explicitly states that "Kagome heals the deep loneliness in his soul". KAGOME. Not Kikyo.
(Granted, I’m not sure how canon that book is, but I do think that there’s ample manga evidence to support the claim.)
"But," you may ask, "what about his constant meetings with Kikyo?" For that, I’m going to direct you to this post. In short, Inuyasha did not visit Kikyo because he was “in love” with her (as Kagome assumes), but rather because Inuyasha either wants to be sure she’s safe or needs to discuss new developments in the Naraku situation.
Remember how Inuyasha was so desperate for his own place earlier? Kagome has become that place for him. He literally calls her his home. She is his inspiration. He feels at ease in her presence. Even as early on as chapter 64, he fears loosing her. He can be himself around her, and she accepts him and loves him for who he is, not for a fantasy of what he could be.
If you haven’t already, please read this chapter. It’s HUGELY important character/relationship development for these two that was entirely left out of the anime (the anime actually tones down their relationship a lot while simultaneously ramping up InuKik’s because LUV TRIANGUL DRAMA.)
InuKik was based on selfishness: two people trying to fix their own problems through the other.
InuKag was based on selflessness: two people genuinely concerned for each other’s well-being.
And lastly, you don’t claim that someone is born for you, and you for them, if there’s someone else you love more.