Wow I've actually given a lot of thought to romance in games for a long time, finally nice to have a place to voice them.
I definitely love having them in games though like many I hate when they feel shoehorned in or tacked on as an afterthought, especially when the rest of the game executes awesomely. Though I don't agree with the sentiment that romances don't work in player created PC/NPC games as well, to illustrate this I'll point at Skyrim.
More specifically a mod called "Vilja in Skyrim".
Marriage in Skyrim is terrible, 'nuff said, we all agree, moving on. I found this little companion mod gem called "Vilja in Skyrim". She has fully voiced dialogue, a rather long quest chain, and tons of comments on everything you could think of, from meeting certain important NPCs, to the weather, to where they are, to how you handle yourself around her in a fight. She actually develops a growing fondness for the PC over time and can even develop a strong love with you. Here's the thing, your PC is given a chance to define their personality far greater in this mod than in all of Vanilla Skyrim because you can put a voice to your actions and dictate how exactly you want this relationship to blossom. All of this and as of the latest version you can't even marry her yet, but despite that you won't want to marry anyone else after playing with her because she's so much more real of a character than anyone else in the game.
Back to Earth, sorry for my mod salesman spiel (hey it's free!).
I think the best place to look for in terms of "romance done right" is Visual Novels, hardly a game on their own, but they incorporate a specific feature common in many RPGs, which is multiple choice text prompts. If an entire convincing story can be portrayed through static images and text with only a handful of "choose your own adventure" style options, why can't you put that in a whole game? There's a great bunch of VN/RPGs made by a company called Winter Wolves that does this very well that creates interesting, though basic in design, RPGs that have that full on romance plot viability.
As much as I love the Harvest Moon games I agree it's time we depart from the gifts buys affection model of video game romances and start to see a realistic approach to it where NPCs and PCs are not blank slates, they have their own personality which can clash simply based off what you say and more importantly, what you do in the game.
Another great game to look at is Mount & Blade Warband. Not so much the romance but the interactions you had with your special followers. You had NPCs who genuinely didn't like each other, they had fights you had to resolve, they would be happy or upset at how a battle turned out, displeased if you were fighting too much, or razing too many villages. They had real honest personalities and if you pushed them too far, they left you. If you handled romance in a game the same way, it would be great.
