I think Jacob likes Bella so much because if anda are a boy and anda have a friend that's a girl anda will start to notice that anda have feelings for her. That's only if anda two have been Friends for a long time.
It's not really something which can be explained. People don't exactly choose to Cinta someone else. Some peminat-peminat theorise that he was drawn to her because she was related to his future imprint though, similarly to how Sam dated Leah before imprinting on her cousin.
