Who should Ryu choose?
In my opinion it should be Ami since she's the best match for him:
Taiga Aisaka
Taiga is more like a daughter to him, the way he's always worried about her and doesn't want to see her in pain shows a fatherly love towards her.
In fact, the only hint of anything other than that was shown on episode 22 but i think he was just looking at new possibilities after getting dumped by Minori.
Minori Kushieda
Minori is always hyper, so much so that it makes her really annoying to watch so i don't really like her character but even if i did anyone can see that their personalities are just too different.
Besides, he would have to be a masochist to have yet another go at her after having been dumped 2 times already.
Ami Kawashima
Ami is a tsundere, no question about it but that's just another reason why they make the best match. If i had to compare this couple to any other it would probably be Toshaka and Shirou from Fate/Stay Night because of the similarities in their behaviors so anyone who has obtained the true ending on UBW knows that those two types of personalities just "click" very well ( in the world of anime/videogames at least ).
Even if we put behind the fact that she's drop dead gorgeous, from the 3 she's the one who has consistently shown an interest in Ryu and yet never changed her personality and that makes me like her even more.
The only reason he hasn't considered her is really because of all the teasing she gave him when they first met, but i believe that after she plainly confesses her feelings towards him she has a good chance to be with him.
Well even after all that I'm pretty sure he'll end up with Taiga ( if the name of the show wasn't a big enough hint for you ) so this is more of a " what i think should happen post " than anything else.