Romances that serve some greater purpose by adding some relevant new layer or POV to the story are okay. Think of Morrigan in DA:O. This bitch had her own agenda and reasons for wanting to hump you silly. Reasons that would eventually intersect with game's main storyline. I could never be against something like this as long as it is written cleverly.
....But then,there is this vast creepy oozy wasteland of terrible completely unnecessary fan service romances that exist for sole purpose of generating them sexi times and Roswellian teen drama. You know, """"!! MATURE CONTENT"!!!" In context average horny teenager has for the term. Add one, just ONE romance like this to any of your games ever and your forum will, for rest of the eternity, have this small, loud subcommunity of creepy people who write 100 page fan fiction stories about Shepard's oily barrels.