Comparison:
Mass Effect:
Straight Male Shep:
Ashley - Your average military woman, firm, sturdy (not literally) but also poetic. Shows a lot of interest in a romantic attachment. Problem being she's racist, stubborn and doesn't hesitate to doubt Shepard about "bad" things he was never responsible for.
Miranda - Professional woman, very attractive, feminine, smart and strong. Romantic attachment's give her anxiety at first. In her heart she's also insecure. Sad romance for both games since she's still afraid of a real attachment. On the other hand she's also pretty cocky and arrogant, obnoxious to some people even.
Tali - Nerdish girl, cheerful, smart, young, shy. Very romantic and uplifting.
Jack - Messed up past, messed up currently, violent, very sexual, when she opens up it's really quite a sad story. Gets over it in the following game and becomes a lot more .. Together while keeping a positive attitude and uses her violent nature for good. But she may seem too repulsive for lots of people's tastes.
Straight Male Hawke:
Merril - Is actually really really messed up but manages not to whine 24 hours a day about it since she's somewhat deluded. She's still very cheerful even if she breaks down a couple of times. But again she's a blood mage, she knows what she's doing is wrong yet convinces herself its right, which again is messed up.
Isabela - Pretty obvious character, light hearted, sarcastic, has a heart of gold, sexually driven, afraid of attachment but Hawke seems to be a special case. Problem being is that she's REALLY greedy and selfish, also sleeps with everything that moves...
Now straight female Shepard:
Kaidan - Very normal guy in Mass Effect 1, has a much sadder past than Ashley however, decent romance but I understand if some girls found it boring.
Garrus - Badass, strong, light hearted,is secretly a romantic and his shyness when pursuing a relationship has very good contrast with his character.
Thane - Sad past, sad present, non-existent future. A very very emotional and tragic romance. Excellent character driven by guilt to do as much good as he can before his death.
Jacob - Very shallow character, good-guy (again) but add to that he cheats on you...
Straight female Hawke: (too lazy to go in depth for either of them)
Anders - Whine, whine, whine then terrorism! Yay.
Fenris - Whine, whine, whine then I HATE MAGES, I'M ALONE HUR DUR DUR
I'll just let you judge now.