Digital: A Love Story is one I played recently and really really appreciated. It's also free so anyone who is curious to try it has no reason not to. Go Google it! The Author has also written 2 other excellent visual novels, but neither are really romance centred, more using romances you're made aware of as a plot device. one is also free, "Don't Take It Personally Babe It Just Ain't Your Story", and another is available cheap on Steam, "Analogue: A Hate Story". All are implied to be set in the same universe.
On the subject of visual novels, obligatory Katawa Shoujo mention, especially Rin's story. Emotional as hell and arguably more about dealing with mental illness than romance, but still and incredible story.
I think in general games are really lacking on the well-written-romance side. Trying to remember some notable examples here. All of Catherine is an instant win for being very believable and relate-able, yet still filling that Atlus quota of complete insanity towards the end.
And speaking of Atlus, a lot of the romance side-stories in Persona are pretty opinion based, but I think the romance stories in Persona 4 were never horrible, and some managed to be really good, with my personal favourite probably being Ai Ebihara's. Persona 3 also had an interesting story going on with both Yukari and Aigis, getting very interestingly brought up again for it's sequel chapter The Answer. Kinda like a deconstruction of video game approach to open ended romance.
Time to cut off before I turn this into an essay I think.