I'd probably argue games that 'can' do this well is JRPGs because they tend to be a slow burn and have a lot of small side conversations that are not directly plot related, which allows the characters and relationships to get fleshed out.

The ones that immediately come to mind are FF 8/9/10 but I'm certain there are others.

In games where the romance is like a mechanic and not a part of the story? Hmm that's a tougher question because I think mechanics/gameification tend to ruin the human part of relationship building.

You know what's wild? The answer that immediately comes to mind is Warframe.

Genuinely, I'm not remotely joking, Warframe has some of the best video games romance I've ever encountered.

Two things really stand out to me about the conversations in Warframe.

First, the things they learn about you are often just as important as the things you learn about them. The article talks about the process of two people figuring out how they fit into each other's lives, and that's exactly what you get with Warframe. You need to actually show that you can be someone they can love, as well as simply showing interest in them.

Secondly, and I think maybe more importantly; most of the conversations in Warframe don't feel "important." They all are. But most of them are about comparatively trivial things. A lot of it is literally just people sharing shower thoughts, or jokes, or talking about dumb shit, or getting things off their brains. But how you handle those interactions matters just as much, if not more, than the heavy stuff.

Also, the way the characters interact feels distinct and different. Amir, the most obvious case of ADHD in the universe, writes five messages for every one of yours (these conversations all happen through "Not MSN Messenger"), and most of the time what he needs is for you to just listen while he unloads all the chaotic shit in his brain. Eleanor, the journalist, writes long, carefully formed sentences with correct punctuation and grammar. She poses questions, prods and pries, tries to dig secrets out of you. Aoi will sometimes just send you a string of emojis, and will be delighted if you reply the same way. She likes to be silly, but more importantly she needs to just know that you're there and you cared enough to reply. It's the written equivalent of squeezing someone's hand. Some characters will pester you, others are more likely to wait for you to talk first. There's a unique dynamic with each of them.

Depends if you want to include actual romance games into the evaluation, because those are entirely dedicated to romance itself, making games like Baldur's Gate hard to compare against.

DayZ. The warming embrace of the games player base envelops you like a warm blanket.

I agree with the other comment about Haven, but I'll also plug in Potionomics. It's more gamified in terms of giving gifts to the chosen NPC you wanna court, but the voice lines and the way the love interest acts feels fairly natural in my opinion. And nothing ends after kissing, it just becomes deeper.

Buuuut that's just, like, my opinion, man.

only one right answer here

For involving the PC i'd say nameless one and annah in planescape torment.

Good banter , good complementary skills (i'd usually focus on magic in pst and have annah do the sneaking around and lure them into the blast zone ), some teaching/learning, some anger, some grief, mutual dependency / ass saving; literal resurrections of course; some infidelity possibilities or at least jealousy. And , of course, you can get the tattoo even though she's scared of the tattooist.

It wasn't plot linked as the other stories involving Deionarra and -spolier- and arguably not even necessarily a meaningful romance, but really good interpersonal dynamics over the course of the game that make the adventuring group more than just a collection of bashers walking from a to b.

Actually retrospectively -spoiler- might also be a good answer even if it was a bit unrequited desperate and mutually destructive. maybe i just really liked that game. I haven't played many modern games though.

Ellie and Dina in The Last of Us 2 maybe?