Osanai is certainly the most compatible with the MC.... as a friend. They have common interets, they have fun together and are becoming more and more intimate.
But that isn't necessarily enough. I'm sorry for her but affection and romantic interest just doesn't work that way. You don't tick a column of requisites and then fall in love.
In fact, many people crave to have a relationship with someone that has the traits they themselves lacks and yearn for. And our otaku likes the energetic, extrovert, busty gyaru.
Also, as he was already interested in Kinjo before meeting Osanai, it's even harder for his feeling to transition from "friendly" to "attracted".
As a side note, my personal preference (taking into account looks and personality) would be: Otomore>Osanai (looks too much as a child)>>Kinjo (hot but boring)>>>>>>>>>>>>>>>>>>Himekawa (not even that hot and she is just nasty).