I was reading a Gamasutra article about this topic and wanted to see what you guys/gals think about it. The gist of the article is that in most games, romances are scaled at "1 to maximum number" but instead of doing that how about you add more variables to the mix.
"It gives you the idea that you just want to be really nice and tell people what they want to hear," noted the writer. "But life doesn't work that way... You're gaming the character instead of engaging with them."
He suggests that you use Rivalry and Respect as the two variables.
At the beginning of the game, the person may feel like a rival to you, but as you both go through specific scenarios, you slowly find respect for each other and the rivalry dissipates, allowing the potential for attraction. What this means is that, rather than just doing good things to your potential romance interest to make them fall in love with you, you might choose to go against their wishes at times in order to later gain their respect through your decisions. This also provides the opportunity for insulting and taking cheap shots at your potential love interest as, rather than putting them off as in most games, you end up stoking the rivalry and it may pay off in the long run
My take is that relationships are messy and rarely make sense. Translating a "real" feeling relationship would be hard to do unless the storyline was already there for them to fall for you in the first place. For them to fall for you based on your actions makes things complicated but I feel that the idea of a two variable method might make it more realistic feeling than "if i worship them and do what they want from me then that will make them want me and they will be mine" which is typically a huge turn off for most of the opposite sex. They want a challenge not a puppy dog.
If I might suggest something else to add to the mix, a third variable which is simply a random number that continuously changes to represent the spontaneous/sporadic element of falling in love. It could be a high point for you two, getting along well & challenging each other at the same time but that doesn't mean that you'll fall in love. In my opinion, this would be the closest to realistic a relationship in game can be.
I'll leave you with this: What do you think about this concept? Is being that realistic even fun/worthwhile for the player?