Or has it always been Dinah?
Aquaman and Hawkman had love interests w. powers, Batman had Robin.
Most DC characters had memorable civilian love interests though.
Superman/Lois Lane
Wonder Woman/Steve Trevor
Flash/Iris West
Elongated Man/Sue Dearbon
Atom/Jean Loring (ugh)
Martian Manhunter/Diane Meade (mostly UST)
Green Lantern/Carol Ferris
For having developed such a horndog reputation, I can’t remember anyone for GA before Dinah.