Jess could have been the best boyfriend (and he is)
By process of elimination, Jess is Rory's best boyfriend. No, I'm just kidding! He actually, really, and truly was the closest thing Rory has to a romantic soulmate. From the minute they met, it was just like they immediately knew each other on a spiritual level. They got each other. But that doesn't mean their relationship was easy.
Jess wasn't a big communicator. He rarely opened up about his feelings, and when he did, he grumbled about it. (The grumpy nephew doesn't fall far from the grumpy uncle.) In my opinion, that was the biggest hurdle Rory and Jess had to overcome. Rory grew up in a house where they talked about their emotions and valued those perspectives. Jess barely grew up with a stable parental figure.
Their differences were part of their attraction, part of their power. But their similarities were what so few people besides them and the viewers had the opportunity to see. Rory seemingly spent so much time fielding questions as to why she was interested in Jess, but the audience knew why. It wasn't just that he was handsome and elusive. It wasn't that they just liked literature. It was something chemical and unspoken.
If he hadn't become "the one that got away," Jess could have been the best boyfriend on a whole different level. The love of her life! No matter where they ended up (which is not together), no one can argue that when it comes to compatibility and how Rory felt, Jess was the best boyfriend. He's unbeatable. For as much as he broke her heart, I'd venture to say he loved her the most.
All seven seasons and the revival miniseries of Gilmore Girls are available on Netflix.