This question is way more fun for me to answer then it probably should be.
Rory is by far the easiest to place: she is a Ravenclaw, pure and simple. Arguably her most defining trait is her intelligence, and though she has aspirations, she loves learning for it's own sake. She's passionate about books and is a voracious reader, something most Ravenclaws have in common, is clever, and though she's not necessarily 'creative' in the way we might usually think of the word, she has what I would consider to be a creative outlet in writing. Early seasons Rory was also shown to be wise beyond her years in many ways. I think it's safe to say that Rory values knowledge above all else. Case closed.
I think that Lorelai is a Gryffindor. You could make the case for her being a Slytherin, since she can arguably be manipulative and ambitious, and certainly she can try to charm people to get what she wants (though it's usually in a playful way.) You could also make a case for Ravenclaw, since she is quick, witty, a walking encyclopedia of pop culture references, and quirky. In the end though, Lorelai went through with her pregnancy, left her parents house, struck out on her own, and worked her way into a comfortable life on her own terms. She is nothing if she is not brave, determined, and stubborn. She also always does what she thinks is right, and is not afraid to be blunt. At her core, she's a Gryffindor.
I don't really know what to do with Richard and Emily. Probably they are Slytherin, since they are ambitious and concerned with their position, and also willing to manipulate to get what they want..and not in a playful way like Lorelai. The incident of Richard cutting Jason out of the business to make the unpleasantness with Floyd go away..pure Slytherin. And yet, underneath that, there is a good deal of Ravenclaw in Richard..he is completely on Rory's level with his enthusiasm about reading and learning..just look at how much nostalgia he feels for his time at Yale. In Emily I can sometimes see some of the Gryffindor traits that her daughter possesses.. certainly in the revival she was brave and blunt. It probably helps that I think that Lorelai and Emily are a lot alike in personality, it's just their life circumstances that are so different.
Luke is textbook Hufflepuff..loyal, kind, humble, hardworking, puts other's needs before his own, always tries to do the "right" thing. In fact I would place most of Stars Hollow in Hufflepuff...with the possible exception of Lane, who though she has some Hufflepuff qualities as well, was brave enough to strike out on her own and persist in being herself despite her love for and deep need to please her mother. Lane might be a Gryffindor. Oh, and Taylor. He's as Slytherin as they come.
I'm torn on whether Paris is a Slytherin or a Ravenclaw. She's so very intense and ambitious and can definitely be cunning. She does seem to love to learn underneath all of that though. She's probably a Slytherin, or if she's not, she's definitely a Ravenclaw hiding under a tough outer Slytherin 'shell'.
Rory's guys..I think Dean's a Hufflepuff. I know people get down on Dean, and I know he can be self centered, but even with the Lindsay debacle I think that in the end he is good hearted, it's just that the Rory situation brought out the worst in him..and he certainly is hard working. Jess is probably Ravenclaw. He is a secret lover of learning, and as Luke said, "reads more then anyone I've ever seen." He's just not a conventional learner..and Ravenclaws are unconventional. My choice for Logan is probably controversial, but I go with Gryffindor. I know most people would probably say Slytherin..but honestly, I think Logan is a pretty upfront guy. He's not really cunning, he's just smart. He is blunt. He is definitely chivalrous. He is a bit self destructive and conceited, but I can see these traits as belonging to Gryffindor. Several times throughout the series I thought he displayed bravery, foolish bravery though it might have been. I also am of the possibly unpopular opinion that there are a lot of similarities between Lorelai and Logan.
