Forget "I love you." That line is the finish line, not the race. The best romantic dialogue is the subtext.
The most revolutionary romantic storyline in the past decade is Normal People by Sally Rooney. The plot is simple: two Irish teenagers communicate poorly, have sex, and go to college. There are no car chases, no amnesia, no vampires. Yet it is devastating because Rooney understands that the most dramatic thing two people can do is misunderstand each other.
how to write exciting romantic fiction | National Centre for Writing | NCW