This is a matter of preference question I take it. Personally I'd prefer he didn't marry any of them, buuuuuuuut........ then again he'd be a lonely guy. I'd say he would sooner her marry Kikyo only if she was never murdered, but she was so the over all answer is Kagome, meh.

exactly sesshy, if kikyo was still alive then the answer would be obvious, and since the question didn't state whether kikyo had to be alive or dead then of course he would pick kikyo. now to be fair i love kagome to and if it was the dead kikyo then yeah inuyasha would pick kagome :P

Well, I think he'd never be able to make a clear choice if both girls were alive and willing to wait for him. He's been playing both sides.
Anyway, it could be taken into consideration that Kikyo herself said that Inuyasha seem to be more concerned about Kagome than her.

KAGOME!!!!!! OMG ITS OBVIOUSLY KAGOME I MEAN KIKYOU DIES??!! SO ITS NOT POSSIBLE!!! kagura? there is no chance and once again shes dead.... and sango? doesnt her and miroku end up together??? SO ITS OBVIOUSLY KAGOME! OSUWARI AND OUT

Even is Kikyo was alive Inuyasha would still chose Kagome ^-^ He loves her with all his heart!!! She loves him too :)

Of Course It's Kagome!! She is the one who has been stayed with Inuyasha and fight with Inuyasha and did everything with Inuyasha. She loved Inuyasha more than anything in her world. Kikyo was Inuyasha's ex-lover, she was once Inuyasha's true love but they lost it. Sad thing is that she can't get back what he has lost, too bad.

So I assume this question means that every choices are possible (if the author really want to do it)
My choice would be Kikyou for being a wife.
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==> Kikyo's care: She is calm and gentle. She will always be by your side (even when she seems not there). However, she will know and come right in time. She will calmly ask if she thinks the situation might be really serious. For the rest, she lets you be free, more independent. While Kagome seems to stick with you 24/24 and want to know everything about your little acts.
==> And for Kikyo's mind. She is realistic and clever. She can give out solutions with far-good perspectives. She does plan so well. Of course, I think sometimes she should try to do somethings seems to be impossible tasks. However, if you still want to do it, she lets you do it. She fights with you. In a long term, she surprises me far enough with all her views. While Kagome seems to: Let's duel with what we see first. Quite a simple mind.
However, to be honest, in reality, men find their self-esteem & their talents are easily proved in front of a heroine as Kagome. Kagome showed clearly that she needed Inuyasha’s cares & protections; she started with 0 in talent and grew together with him.
Kikyou didn’t act like that. Men feel hard to see & understand Kikyo's love as well as hard to prove themselves in front of her. So not every man can understand and handle a woman as Kikyou. Still I personally think her act was because of her duty and her death.
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For not choosing InuxKag: My reasons are, in real life:

*** On Inuyasha’s side: Inuyasha is so dump around Kagome. He's simply a boy much more than a man. Inuyasha hardly stays calm to think through deeply Kagome's words. He basically just understand the surface and her face's expression. However, he still did it first then felt sorry later. I barely see his mature mode around Kagome in daily occasion. Mostly, it only happens after big events.
He showed less desire as an opposite sex partner to Kagome. I know their relationship based on friendship. But it didn’t mean that there should be lack of desire for kissing. And after being apart for 3 years, all his doing is hugging. In the manga, they didn’t kiss even once.
*** On Kagome’s side: I find Kagome has a hard time to explain things out to Inuyasha. Probably, she would say… as a threat or an order to make him really listen. In the series, we see that many times. In Inuyasha's CD - which describes their life after original series, Kagome recognized that Inuyasha didn’t propose to her at all. However, she couldn’t even explain to Inuyasha what proposal is even though she had tried to… And end up saying “osuwari”.
*** InuxKag's relationships will work in dating mode. They hardly calm and talk things out. Yes it’s hilarious at the beginning. But as far as the story went on, I felt it tiring. And after all their fighting, especially in serious cases, usually, Kagome would end up saying “I want to see you”, “I want to be with you”, “Let’s me be with you”. It’s always her. Because she loves him so much. In the last chapter, Kagome was the one who thought that “I want to be with Inuyasha” to reconnect their time back. Again, it was from her side.
===> Personally, the only reasons that I see InuxKag could work out is all thanks to Kagome.
===> So I find InuxKag hard to work in real life. The relationship hardly last long with someone who couldn’t consider you in a deep way of thoughts; someone that you find it hard to explain things out. Because you had to deal with every little problems in a harsh way. But if you enjoy fighting, then it’s fine.
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If you argue with me that Kagome changed him to believe & act softer to people around. That Inuyasha did have mature times around Kagome. I must say Kikyou could do it even better without “osuwari” if she was still alive. There’s no need for big circumstances, his daily life actions showed he could consider Kikyou in a very deep ways. (He listened to Kikyou's words more calm and carefully. He protected what she protected. She easily brought out his guilty mode. She could stop his actions just by gently calling out his name. He less went again her words. He gave her a gift from his mothers...) Kikyou easily bring out the man in Inuyasha without even asking for it. And Inuyasha had his most desired embrace & passionate kisses with Kikyou.

Personally, I don't understand this fandom:
+++ When Inuyasha yelled at Kagome nor acted cool nor tried to hide his caring & jealousy for Kagome. His immature actions become Inuyasha is being himself. While I've always wondered about how much deep is his feeling? It couldn't over come his self-protection because he choose to protect his pride over the love for Kagome. And what's kind of being true-self when he couldn't even show his true feeling?
+++ However, when Inuyasha acted gentle around Kagome, they said it's love and romantic. When Inuyasha acted mature when Kagome returned to her home. They said it was the proofs for the growth of love, the true love. Why didn't they said that he isn't being himself? It's opposite with their above argument.
And after reading through all their explanations for InuxKag's relationship. They gave me the opposite understanding for InuxKik's. Whenever Inuyasha acted like that around Kikyou, their only saying is: "Being Mature" and "Being gentle" equaled to "not being himself" and "guilty". Why is that ???!!!

And If it's only from guilty feeling, I find it hard to understand why:
*** Even when Kagome had doubts about Kikyou, Inuyasha still kept on believing Kikyou. I’m not discussing about love or guilty. What I’m trying to say is Kagome’s opinion meant lesser to him when it came to Kikyou.
*** He said things as “if his life belongs to her, then her life belongs to him as well”. This was simply an arrogant, selfish declaration. If he only felt guilty, I don’t understand why would he say that?
*** He could run to Kikyo and leave Kagome (sometimes, even without a word to Kagome).
*** He wanted to have all the privated times being with her.
*** Even in front of people, his eyes hardly took away from Kikyou. Sometimes, I see him only looked at her deeply. Let’s think for a moment: Do you find it easy to look deeply in someone’s eyes when you only feel guilty (especially when you still couldn’t return the favor)? The eyes hardly tell the lie.
*** And in Kikyou’s last moments, I’m sure that everyone wanted to have a word with her after all that she’d done, but Inuyasha wished to have all of her time for himself. Personally, I only see the way he spent with her in last moments just happened between lovers.
*** He could give up everything even his life for her. After her true death, he would have died without Kagome’s voice. He never answered that he wanted to go after her or not. Kagome knew he did want it.
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You could argue that InuxKik’s feeling was easily tricked by Naraku. You should consider the circumstance:
+ They started technically as enemies: a priestess and a demon, a guardian of Shikon Jewel and a demon who want to steal it.
+ It happened in a very sensitive case because they just technically proposed to each other.
+ They didn’t stay with each other 24/24. They had their own life. So they didn't see anything before the attack.
+ That was the very first problem that they had faced with each other.
+ The high level that Naraku had made them been through: To be attacked in a very serious mode without knowing that they did have a very dangerous enemy.
=>To ask them to keep their mind clear. I’m sorry, it hardly happens in real life.

InuxKag was built up from the easy state to the harder one.
+ They were just a mere human and a demon. And what would Inuyasha have if he attacked Kagome? And why would a mere future girl want to attack him? And she has already had the necklace around Inuyasha’s neck to control him.
+ They said nothing about their position to each other
+ They had to stay & work together 24/24 to find the Shikon Jewel.
+ They faced from small problems first. And at the first time they were attacked by each other, they saw the different changing because they technically stayed with each other 24/24. They had not been attacked out of nowhere.
+ Inuyasha knew the truth in his early journey with Kagome: They knew their main enemy.
=> They didn’t jump in a high level condition. And mostly, their status was nothing to each other.

In the end, I must say: Kagome and Inuyasha were chosen by fate to spend all those circumstances together. The rest is the matter of time, but Inuyasha & Kikyou didn’t have that either. When Kikyou was revived, the only reason why Inuyasha and Kikyou could never work out was because she dead and her body wasn’t real. If Kikyou was actually alive, things definitely would be different.
Life isn’t fair. That's why.

People say she changed. She wasn’t the same person that Inuyasha felt in love with.
But did she? The core of Kikyou’s characteristic: being a miko, fighting with evil, living and full filling her responsibility, helping the village, healing people, playing and teaching children,… loving Inuyasha even though she had always acted cool and pushed him far away. Which one of her was changed? I agreed that she had done wrong. When she was revived, she acted towards hatreds; she was cool, wicked, … However, every main (main-sub) character in this manga had done wrongs (except Kagome), people forgive them all but not Kikyou. The greatest example is Sesshomaru. Oh, is it because her look was kind & gentle when she was alive? Then I suppose you’re asking her to be a happy dead corpse then, are you?
Kikyou’d done all those cool reactions for Inuyasha sake. Naraku would feel happy and easiy to deal with all of his enemies was then in one same place. And if she just wants to simply have or drag him into hell with her, why would she be there by his side? Why would she choose to fight alone? People ask her to just die. Seriously, saying as if they would choose to die meaningless without trying to do anything. She chose to fight or even to die while fighting with evil.