Lorelai and Christopher
So unpopular opinion. I think Lorelai and Christopher belong together.
I really like Lorelai and Luke and their chemistry during the first seasons, but when they finally get together, that chemistry seems to be gone. I try to find "aww" moments between them when they start dating and they're really hard to find. I can't even remember if they have an "I love you" moment. I think they worked way better just as friends.
Christopher and Lorelai though, the chemistry is always always there. You can tell their relationship is much more than just about Rory. They've known eachother forever and they just click. Also, they always end up going back to each other one way or another. They are always laughing and you can tell they really love each other. They should end up together.