Well according to me, among all the girls.. Sanjana was the only one who was normal.

By normal I mean she was not representing any social message and was going through simple day to day problems that a normal girl goes through. Neither she was pampered nor was she too open or too shy.

She was kind of the girl next door.

Plus they both had a lot in common and had built up attraction towards each other.

The family also approved Sanjana during the end.

Finally, the movie was about how people belonging to different sun sign's had different personality and characteristics. Many people believe that some sun sign's are more compatible with each other then the rest.

So maybe she was the right girl for him in this respect as well.