Psychologists have long theorized that the relationships we form as adults mirror the blueprint for relationships we absorbed, consciously or not, in childhood. Which is to say, the people we're attracted to as adults oftentimes fit into the same mold that we observed as children; humans have a habit of going with what's familiar, for better and for worse.
Nothing says Gilmore Girls quite like an indulgent psychoanalysis, so let's dive right in and just blurt out that Rory Gilmore loved Jess Mariano because, for Rory, to love Jess is to fall back into the comfort of a pattern she had with her mom, Lorelai Gilmore.
If you sit down and break apart the characters Jess and Lorelai, you will see that they have more in common than you think. For instance, take a look at the way they feel about their families. Lorelai came from a wealthy east coast family but rejected its ideals and lifestyle. When she became pregnant with Rory as a teenager, she ran away from her parents to the small town of Stars Hollow, in order to give Rory and herself a different life.
Lorelai's relationship with her parents is strained the entire show, and they only see each other as often as they do because her parents offered to pay for Rory's private school in exchange for having dinner together every Friday night. Lorelai never felt understood by her parents, and really, neither did Jess.