Admittedly, I have always had high hopes for Lorelai (not to be confused with her daughter, Rory whose real name is actually Lorelai ) and Luke.
Before they even got together, I could sense there was something between them. As the show followed their relationship, we saw them dating other people, and never each other (until the fifth season I believe.) Up till then, they were friends, giving each other advice about relationships and life.
When Lorelai proposed to Luke, I was SO excited. I felt like this was a relationship that could actually last, and a healthy one for her to be in. However, Luke was slowly pulling away from Lorelei, after he found out about his daughter April. Eventually, because of the distance in their relationship Luke and Lorelei broke up. Which led to Lorelai going to Christopher's house and spending the night, which caused even more of a rift.
In the last episode of "Gilmore Girls: A Year In The Life Fall" Luke was incredibly sweet to Lorelai after she came back from her hike, and he thought she was leaving him.
This right here is all I will ever need. I never imagined that in my wildest dreams that it would happen, that you and me, that we would happen. But we did it. Listen, I know I'm not the easiest guy in the world to build a life with, and to share a house with, but there is no one who will be more here for you than me. I will never leave. I will never think about leaving. I will do whatever it takes to fix what's wrong." - Luke Danes, "Gilmore Girls: A Year In The Life" Episode 4, "Fall"
I believe Luke just set the standards high, for every relationship everywhere. To me, this quote just shows Lorelai how much Luke actually loves her. We know that she's had trouble with a lot of relationships before him, and when they first dated they had a lot of problems of their own. However, they always ended up going back to one another.
Now Lorelai knows more than ever that Luke is the one. In the same episode the quote came from, while on the trip, Lorelai had said she thought she knew what she wanted, and where she was headed with her life. But now, she wasn't sure at all. Which led to them getting married, and actually going through with a small ceremony.
Luke saying what he did, must've definitely made her feel more grounded, and supported. Which I think is what everyone needs from time to time, even if they won't admit it. These two have always been there for each other, even when they weren't speaking.
I guess you can say, Luke and Lorelai bring definition to relationship goals.