I'm just going to talk about DA romances, because I only really know them well enough and, really, DA romances are what matters in this forum.
Female Characters;
Morrigan -
She was raised by Flemeth in the woods, what could be good about that? She believes her mother is setting her up to steal her body and her mother is the only person she's ever really known more than brief encounters. She has an extreme distrust of men, especially, which comes up often. She eventually gets pregnant and runs away, or just leaves if you refuse the pregnancy/ritual.
Leliana -
Her ex-lover, Marjolaine, betrayed her and left her to die, which lead to her undergoing a faith based epiphany. A big part of her character arc is hunting down her ex and possibly killing her. Like Morrigan, she openly talks about manipulating others, which makes it difficult to trust her completely. It's later implied she's basically a spy for the current Divine.
Isabela -
Her mother converted to the Qun and sold her into marriage when she wouldn't convert, as well. She had her husband killed (by Zevran!) and she stole his ship. She's an ex-slaver that drown a shipment of slaves to save her own ass. She has extreme difficulties trusting or commiting. She's selfish and some things she says in DA2 are shown to be lies in other materials. She continues to sleep with other people while in a romance.
Merrill -
She feels like an outcast in her clan. To compensate for her inability to connect, she obsesses over the Eluvian, thinking she'll give something back to her people and they'll eventually understand. All the while she pushes them farther away and this just intensifies her obsession. Eventually this obsession destroyed her tribe and never even paid off with a fixed Eluvian.
Male Characters;
Alistair -
Royal bastard who was basically pushed into the templars. He was forced to oversee a Harrowing where the mage had to put down and it seems to have made him bitter towards the templars. He seemed happy to join the grey wardens instead and looked at Duncan as a sort of father figure, but all the wardens he'd connected with died. He fears responsibility and doesn't like to lead, but he's being expected to challenge the throne.
Zevran -
Groomed from a young age to be a Crow assassin. He killed his ex-lover and then found she was innocent. It's implied the man that comes to ask him to return to the Crows or kill him otherwise is also an ex-lover. He has trust issues and trouble commiting.
Fenris -
Ex-slave that went through an extremely painful procedure that gives him unique powers. He has amnesia, but later finds that he fought for the opportunity to get the lyrium brands in exchange for the freedom of his mother and sister. His sister sells him out to his old master. He has issues with intimacy and is extremely broody. His romance is much harder if you play a mage, do to his extreme vitriol towards them.
Anders -
All he ever wanted was a free, simple life, but he's been hounded by templars trying to keep him locked up since he was young. He gets drafted into the wardens, which is just another form of loss of freedom. He merges with Justice to try to help the mages. In Kirkwall he sees extreme abuses inflicted on the mages and can still do little about it. Eventually he snaps and blows up the Chantry to force change.
Sebastian -
His family was killed and he flip-flops on killing those who killed them, then on whether or not to take back the throne from those now holding it, or to stay a brother of the Chantry. He has a past involving a lot of partying and such, but now he's extremely religious. He's pretty immature and can never seem to make up his mind about anything. He's a chaste relationship, which many people don't like. Eventually his mother figure is killed in the Chantry blast and he demands you kill Anders or he'll leave, ending the relationship.
Basically, these are all extremely troubled people with very rocky pasts. There are no LIs in DA with "nice" backgrounds. In Origins the only LI that doesn't have obvious ulterior motives is actually Alistair. In DA2 everyone is a HUGE mess. I don't think you can expect DA to always try to make up for things the ME team has done. They've kept it pretty even in this regard. In fact, females had one more LI than males have had, overall. I wouldn't honestly worry too much about DA being fair to straight women. I think they've been at least fair, thus far.