The best love story I know is my parents. They have been together since they were 13 and 15 and have never had any other significant others; my grandparents were iffy about my Dad and my Mom had to beg for months in high school to be able to go out with him. My grandparents were also dismayed that, while my Mom married in her home church, she eventually switched to his church and denomination.
They married at 19 and 21, are in their mid-60's now, and are still happily married. They were told they would never have children, resulting in them adopting me, then a few years later, my brother, and finally... my little brother ("homemade", as Mom says) defied all the doctors predictions.
I know different things work for different people. I wish I could have had the same kind of story, but it has not worked out that way.
But for my parents, their marriage has grown from a simple love story (their first house was a $5000 trailer and my Mom said she thought they'd be living there for the rest of their lives) and has resulted in a very cross-cultural, multi-dynamic, amazing family story.