The article that Johnny kind of linked makes some cogent points about how "romances" tend to work, in that they really don't. Their function is an extension of RPG narrative and quest design, and sex is often the payoff at the end of a long period of making the right dialogue choices time after time. It's something of a minigame in that. Especially in Bioware games since KOTOR there really is the sense of "keep talking to me until the end of the game and then we'll have sex". In The Witcher it's actually a trading card game, not far removed from the sort of thing that you'd imagine a frathouse setting up.
Thus these game romances, like all mass media, play into the idea of sexuality, particularly female sexuality, as an exchange of power, a competition over who can control the commodity of a woman's virtue. By placing sex at the end of the character's story arc they (perhaps inadvertently) play up sex as something that you're rewarded with for making the right choices, something that you earn. The problem with this is that it creates an expectation. I remember when Vampire: The Masquerade Bloodlines came out, and for all its faults it was actually pretty progressive in having several outwardly sexual female characters, only one of which it's possible to have in-game sex with (mostly because she's bored and does things on a whim) Anyway there was a sizable amount of griping on the part of gamers who felt that these female characters who were dressed provocatively and often teased PCs should have been available as potential conquests. Their contention was that it was pretty obvious that these characters were interested and it was dishonest to not actually make them interested. Attitudes like that are common inside and outside of the context of the game, but they're reinforced by the way that games usually play out. Games obviously aren't solely responsible for these expectations, but they're part of the apparatus that encourages them.
The article was brought to the attention of the Alpha Protocol guys (the article is ostensibly about that game) and their counterpoints tended to be either A. the writer had not played the game and thus couldn't make judgments or B. It's an incomplete criticism to say that male characters have a tendency to dominate female characters in games when male characters have a tendency to dominate anything and everything in a game world, including the laws of physics and other male characters. There's something to those arguments but they don't quite seal it for me.
Anyway, game romances don't seem to serve any clear purpose beyond titillating players. The way games are structured makes naturalistic progression of relationships more or less impossible to portray (actually The Sims, with its elementary school level of understanding of sex, inclusion of mundane life and freeform structure, comes closest) and thus I don't think there's a good reason for them to be in games at all, besides the fact that they appeal to common fantasies (particularly about the type of women who seem unattainable) and move units.
As for BG2, it doesn't have romance, it has extensive rehab therapy with sex at the end. I never tried Anomen's arc with a female character because Anomen's VA and writing were generally pretty annoying.
