I think that the reason game romances, and Mass Effect romances particularly, have such high expectations is because the gaming technology has evolved so much. The player is injected into the game environment and drives the story as if he is actually living a motion picture. He interacts with interesting characters, he makes decisions that have an impact on the story, and when it comes to romance the player naturally expects more from a game where every other dimension of the game story has been enhanced.
If you go back a couple of years and track the comments there is a consistent demand for more NPC interaction and character development and romance goes hand in hand with that. You meet an NPC that you like, you flirt, and then you take it to the next level in the game environment. With quality voice actors and the level of sophistication of facial expressions and body movement it really isn't hard to understand how someone would want to explore just how deep the romance part of the story could go, particularly over a set of games where the player character can be imported with his decisions, romances, etc.
If you follow these boards at all, you will find threads dedicated to individual characters, threads discussing character biology, and even the fertility of characters. That means that there is a serious fan base. However, merely asking the BioWare devs for better romance hasn't returned any serious results as of yet and I am hoping that ME3 will correct that. I would recommend going to Spike and any other awards people and encouraging them to add a romance category to their list of awards for games.
I think that stimulus will finally drive what the fans want in their games regarding the romance side of the story because the games developers will try to shoot for that target in order to add another trophy to the mantle. Further, it would also provide another dimension for the voice actors to explore, further fleshing out their characters. Of course, this would likely add a few more dollars to the cost of the product, but if it were done right I would spend my money for it.