I am a firm believer that romance is relative. It has to be. People are different, relationships are varied, and so the qualifications for a gesture be considered "romantic" must be adjusted for each situation. Romance is, by nature, very personal. The more personal and thoughtful the gesture, the more romantic it is (or else the more potential it has to be romantic).
Yes, indeed, romance is relative. And that means three very important things for writers.
1) You have to know your characters.
If the criteria for "romantic" changes from individual to individual and from situation to situation, then you absolutely, positively must know what makes your characters tick in order to write them in a romantic light. Not every girl likes a dozen red roses. Some prefer tulips or lilies. Not every girl likes chocolate. Some prefer caramel. And even though "romance" usually revolves around the female's criteria, what is "romantic" for the male character? To write a realistic romance, you need to know what makes the characters in question different from others, and you have to know not only what the characters find romantic, but also why. Why does Sally hate roses? Is it because she's allergic? Does she hate the smell? Or was there a childhood trauma involving roses?
While Sara's reasoning for her rose hatred tells us a lot about her, John's reasons for bringing Sally flowers reveal plenty about his character, too. Does John bring Sally roses because he grabbed the first flowers he saw at the store? Or did he research flowers and their meanings and settle on roses as the most appropriate? I have a friend who was ticked off with her husband because he brought her yellow roses instead of red. Yellow is for friendship, not romantic love. (Not every girl would mind, but she did.) The husband didn't do his research. Don't make the same mistake with your characters.
2) You can develop your characters through their criteria for romance.
If John gives Sally a dozen roses, readers will understand that he's making a romantic gesture. However, we don't learn much about either character through this exchange. For an example of character development through romance, I'm going to turn to a TV show. Let's take a look at the Valentine's Day episode of The Big Bang Theory (which, BTW, I thought was totally cute). If you haven't seen the show, then you need to know that Sheldon and Amy are nerds. He's a theoretical physicist and she's a neurobiologist. Neither really understands social norms, although Amy tries. But if you had never seen the show before this episode, both Amy's and Sheldon's romantic gestures would speak volumes of the characters. I'm putting a Spoiler Alert on what follows, just in case you haven't seen the episode yet.
While Amy had been planning a perfect Valentine's Day - complete with dinner and "romance" - she knows Sheldon is uncomfortable with all that. Her romantic gesture is to cancel her plans, order pizza for Sheldon and watch his favorite Sci-Fi show at his apartment. We see that Amy not only cares for Sheldon and puts his needs before her own, but we also learn about Sheldon. "Socially awkward" doesn't even begin to describe him.
Then Sheldon gives his gift to Amy. He informs her that she is now his emergency contact at work. While that may not typically be considered romantic, Amy almost cries with joy. Sheldon has demonstrated that he understands how important it is to Amy to be more a part of his life. As viewers, we learn that Sheldon may be socially awkward, but he does, in fact, care for Amy despite his weirdness. Here, romance is used to develop both Amy's and Sheldon's characters.
3) You can use stereotypical romance as anti-romantic.
Let me explain. We'll go back to the dozen roses, since it's a popular, stereotypical romantic gesture. But if Sally is allergic to flowers and John brings her roses, it's not so romantic. In fact, John loses some brownie points for his thoughtlessness. If she's diabetic and he brings her chocolate, he's really not doing his job. As a writer, you can use what is usually considered romantic to paint John as a jerk. If Sally is torn between loving John and loving Brad, the dozen roses or box of chocolates might be what tips the scales. John brings flowers, but Brad - caring for Sally's sinus issues - brings an edible chocolate rose. Brad wins. John brings chocolates, but Brad - concerned with Sally's glucose levels - brings a lower glycemic index fruit/veggie tray, which he put together himself. If Sally has any sense, she'll love Brad, and we'll love him, too.
The guy who always does the "romantic" thing - i.e. the stereotypical stuff - may not be the hero of the story. He may, in fact, be the villain. But the guy who puts thought into his gift is definitely our hero. It really is the thought that counts. If John is actually a villain, he gives Sally wine before she has to drive on a snow-covered road. Good guy Brad, however, gives her a portable snow shovel so she'll be safe when she's driving alone. (Actually, I totally stole that idea from my parents. The first Valentine's Day gift my dad ever gave my mom was a portable snow shovel, so she wouldn't be stranded on a snow-covered road. It wasn't stereotypically romantic, but it showed a lot of thought, care and concern.)
So romance is relative in real life and in stories. We can develop characters and reveal a lot about who they are by what they deem "romantic". And hopefully we'll wind up with a heart-rending, tear-jerking, Kleenex-devouring kind of story that'll have us rooting for Brad (or whatever his name is) and will make us fall in love all over again.