There are a lot of things about my SO that make me feel loved. The one common thread to all of them is she will put my needs first (as I do for her), or maybe a better way to put it is a lack of selfishness.
A small example is that I work nights and we are in the midst of a cold miserable winter. Last night I was showering and getting ready for work and she said she was going to go start the truck so it would warm up for me. I told her she didn't need to do that (I am kind of old fashioned ). She replied "you would do it for me" and was out the door.
Lack of selfishness!
4 kids all adults.
Married 22+ years.
I have moved on and life is good!