Hmm...
Best:
Enslaved: Odyssey to the West
- Yes it falls for a pretty simplistic guy-meets-girl trope, but it's done in a heartwarming fashion. It's whole, there's no gaping jumps where characters do a logic-defying 180.
Red Dead Redemption
- I don't know if it is technically "romance" since John's been married for a while. But in terms of a relationship it's one of the best I've seen. A committed married man? In a video Game? WOW!
Ok, but flawed:
Dead Space 2
- For all the plot holes (Elie goes from trying to shoot Isaac to willingly babysit a crazy guy for him in the space of about 5 seconds), the characters treat it appropriately, given the circumstances.
Half Life 2
- Alyx Vance is a cool character. But Gordon being a mute kinda ruins the whole conversation, and they try to rush a romance into a series of events that end up being shorter then a single day.
Terrible:
Bioware romances. As much as I love and adore Mass Effect and Dragon Age, the romances ain't it.