Like 90% of the males who played ME1, I went for Liara. I didn't dislike Ashley or think she was Space Hitler (lol played out meme), my paragony-with-a-hint-of-renegade-if-you-push-me Shepard just didn't get it on with subordinates. Plus, Liara was hotter and more interesting as a character.
THEN, I get to Ilium and she has the GALL to tell me "that's not how the galaxy works" when I ask her to join me? Shepard is the Ultimate Galactic Badass (TM) who kills or blows up anyone or anything that opposes him! I was only single-handedly responsible for the destruction of a massive, nigh-immortal, robotic killing machine who was about 5 minutes from ending all organic life in the galaxy, and she thinks I can't find the Shadow Broker? You can't even stop me by blowing up my ship, spacing me, and frying my ass in a planetary re-entry from orbit! Don't give me that crap girl, until 2 years ago you were hiding in ancient ruins because you were naive and socially inept, and NOW you know how the galaxy works?
Oh, and you knew I was going to be alive because you handed me over to the dudes who rebuilt me, and you're STILL gonna ditch me? Two years is nothing to an Asari! Heck yes you are getting cheated on!
So where does that leave me. Since I have no interest in Jack, that leaves Miranda and Tali. In terms of character development they both kick Liara's ass.
Miranda starts as the ultimate ice queen, but once you hit the mission with her sister you start to see the real person inside there. When you finally get past her defenses, I was convinced she actually cared about Shepard. At the end when she told the Illusive Man to piss off because she was sticking with me, that just confirmed it. Doesn't hurt that she's hot, but there's a lot more to her than that.
Tali's had a thing for you for 2 years even when you were dead for all she knew. On the surface it might look like infatuation, but are you gonna risk possible DEATH to be with someone for an infatuation. I think not. Plus if you don't break down and give her a hug on her loyalty mission you are soulless.
In summary: forget you Liara!