You know guys, it just struck me.
I still don't quite understand why I like Tali so much (and Liara, too, for that matter, but that's another story).
Okay, I know that she is dedicated to her people, remarkably loyal, has a good (but not oversized) sense of humor, intelligent, sweet, considerate, independent, (but not overly so), and yet, beyond these rather superficial observations, I still can't quite pinpoint why I like her.
But, nonetheless, I believe that the reason I like her so much is because it is difficult not to like her, particularly when surrounded by women like Jack and Miranda. Now, don't get me wrong, Jack and Miranda are great characters, but they don't come across as immediately likeable, while Tali is likeable from the start (and being a recurring character from ME1 does help).
So, in my attempt to explain my own views, it appears that the simplest answer may be it!