It's subjective, of course, but I do not think that Culver's is as good as In-N-Out. I put them in the same tier as Chick-FIl-A and Shake Shack. More controversially, I also put Whataburger in that tier. To be clear, that's the "very good" tier, and I consider that esteemed company. It's just not the In-N-Out tier.
Regarding In-N-Out, overall, I just really like them for a lot of reasons. Of course, the food is delicious and cheap and kept me alive through grad school when I was making less than $20K/year in one of the most expensive cities in the world. They have also provided steady, enjoyable employment for a lot of my students while they were in college over the years. I also just generally like the aesthetic and seeing one in a neighborhood or along the freeway brings a smile to my face.