There are many events and reasons throughout the series that contribute to Harry's affection for Ginny. In the beginning, he was friends with her simply because of being best friends with Ron. Throughout the novels we see Ginny begin to grow and mature. She becomes a strong young woman and very talented witch. Throughout the fighting with Voldemort, Ginny remains loyal in her friendship with Harry. She sticks by him throughout the events with Dumbledore's Army and the attack on the ministry in the Order of the Phoenix. As the novels progress, their friendship strengthens and they both begin to realize their true feelings for each other. The important part is that is is based on their existing friendship. When you have that friendship foundation in a relationship, you are able to withstand harder situations. Such as the war against Voldemort.
Harry likes Ginny because she is no longer the little girl he met when he was 11; he likes her because she is no longer the little girl with a crush on him from second year who sent him a silly and embarassing Valentine's poem and whom he saved from the Chamber of Secrets. Ginny talks to Harry now, and according to Hermione, she is "over him". Although he still sees her in the beginning as Ron's little sister, the Amortentia tells the truth of his growing feelings as he smells her flowery scent, and the monster in his chest is growing ever more restless as his feelings for her grow. To Harry, Ginny is like a soul mate who has shared some of his same experiences with Voldemort, and she is fiercely devoted to fighting for and with Harry for what is right. She is with him at the Ministry and comes across as his biggest supporter and one of his best friends. All of these things combined with the fact that Harry simply needs someone to love account for the fact that he not only likes, but literally comes to love Ginny.
She's smart, cute, and convenient for three reasons. She is the sister of Harry's best friend, Ron, and Harry is always at Ron's house. She has also helped Harry through a few tight spots when fighting evil. That's always a plus--adreneline. :) Ginny has had a HUGE crush on Harry for the longest time. It's always pleasant to like a person who likes you back.
Harry likes Ginny/falls in love and marries her for many reasons. A few of the main ones include that she is a witch who is loving and supports her brothers, friends, and family. (I personally dont really like Ginny so my answer may be slightly biased) :). Harry needs someone like that in his life, because he usually has no stability whatsoever throughout his time at Hogwarts.
she iz s00 smart and loyal towards harry..from the begining she idealize harry for his fame this idealization gradually turns into passionate love...and in return she got harry likness as well which make their realtion ship stronger though harry first feared that ron maybe upset about this but ron realized that they are for each other.....and if u have read HARRY POTTER AND THE DEATHLY HALLOWS u will come to know that when voldemort brings harry dead(he thinks s0)in howgorts ginny was the first to scream and harry thoughts were"i wanna get up to reply the screams of ginny"
It's not for us to decide. Actually, it is so because J.K. Rowling has written the book in such way.