Let's go case by case:
Hanekawa: In Kizu, Araragi sees Hanekawa as a perfect being. Good grades, good ahem assets, being president etc. After talking with her he starts to love her. As for Hanekawa, I am pretty sure she likes Araragi from the start. Now, we already know how imperfect Hanekawa is. Even in the Kizu, she tries to "gain" Araragi by manipulating him (emotion-wise). The "chicken" scene in Kizu 3 is actually about this however because of the fanservice, people tend to miss this. So at the end of Kizu, both are in love with each other.
In Nekomonogatari, Araragi also sees how imperfect Hanekawa is. To understand this, you might want to check out Nekomonogatari Kuro episode 4. In the middle of the episode before fighting, there is a really good exchange between Hanekawa and Araragi. Yes, at that point Hanekawa is talking, not the sawari neko. Again you can understand it better by watching.
Anyways, because of that Araragi loses his interest over Hanekawa. However, Hanekawa still loves Araragi and finally admits that in Nekomonogatari: Shiro. She is rejected by Araragi thus finally Hanekawa can move on. So this is the basic summary of character development for Hanekawa-Araragi love. Now let's talk about Shinobu.
Shinobu: This is always a grey area for me. Because what he did to Shinobu, Araragi always feels bad for her. Shinobu, of course, is really mad about it too (End of Kizu). That is why she never talks in Neko: Kuro and Bake. I think the best place to start our character study is Nisemonogatari episode 4's famous/infamous bath scene. That is the first time we hear her voice (broadcast-wise). I highly recommend you to rewatch this scene. It tells a lot of things. However the basic idea is, "I am not forgiving you nor you should forgive me but let's move on from that". If you think about it, Shinobu had weeks to think over her situation after Kizu. From now on, they kinda became partner in crime. That "I am not forgiving you nor you should forgive me" becomes their base of this relationship.
I have to skip lots of arcs here because I really can't list all of them but because of their character developments through the Monogatari (for example time travel arc), they start to care each other. Actually, the time travel arc in Second Season gives us a good perspective. Even while not talking to Araragi, Shinobu still cares about him. Let's remember the end of Kizumonogatari: "If tomorrow you die, then tomorrow my life will end. If today you live, then today I will live on". Ironically, even Gaen-senpai, she knows everything, couldn't comprehend the reasoning behind their "taking care" relationship in Owari S2. Please also watch that scene.
So in the end, the relationship between Shinobu and Araragi is a complex one. It is not love as we know but they really care each other. Not in a romantic way. Now for the last entry, I don't have a good analysis but I will try to explain my points.
Hitagi: First of all Hitagi really falls in love with Araragi after helping her. That's obvious. This is happening in Bake, after Neko: Kuro, so Araragi isn't in love with Hanekawa. This is kinda my interpretation but I think Araragi falls in love way after they agreed on dating. Maybe it's really true love or maybe it's Stockholm Syndrome but we know for sure that they really love each other at the end of Owari S2. There is no real development I can talk like above however I believe Zoku Owari will give us a good explanation over this.