Why would anyone anyone enjoy Sansa in the show up to this point? Well ... why not? Because she hasn't killed anyone? She hasn't had a "badass" scene? I mean, is it surprising that the girl who is currently a hostage to the family that not only has she been forced to marry into, but has beaten and tortured her, threatened her with rape, killed her father right in front of her, and now have also killed her mother, brother, and sister-in-law hasn't done anything but try to lie low and not piss anyone off? She's doing what she can to survive - saying the right things to the right people (ie. telling people that she indeed loves Joffrey and wants to marry him, because she knows admitting her hatred would put her in a worse position) and doing her best to stay out of the way in case the family that is killing her family off decides to come for her, too (Say, for example, if she and Arya switched places. Obviously everyone would love if Arya was in Sansa's spot and responded to threats of rape and torture with witty and sarcastic comebacks, or even attacks ... until eventually she was killed. Same with Sansa, she can't survive out in the wilderness, and too would die.). And for that, everyone should hate her? I mean, I could get people not caring about her in the show, especially since they don't have access to her thoughts as they do in the books, but actively hating her as you and many people in this thread do (I've seen people on this site go as far as to wish death and rape upon her), is ridiculous.
I can also completely understand why people would want to like Sansa. She's trapped, alone, has virtually no one she can trust, and (what I find most admirable about her) is that despite all the horrors she has seen and been through, she still hasn't broken and still believes in the things her father (who coincidentally everyone LOVES, despite being pretty much an older, more mature, just as "stupid", MALE Sansa, but that's another issue) taught her, like being chivalrous and believing in being honest and all that "good" jazz. She's still "innocent" and "pure" in that regard. She's like a Disney princess written into the wrong story. She's not power hungry, she's not bloodthirsty, and she clearly doesn't want to play in the "game." Obviously some people choose to see this as stupidity and naivety.
On top of all that, she is probably the most realistic and relateable character in the series. As much as we would all love to believe we're badasses like Arya who will easily kill, and sarcastic, clever, and witty like Tyrion who enjoys playing his role, we're not. Sure they make for interesting stories, but it's part of why I like this series that characters like Sansa are included. Lots of us (especially book readers I guess) would probably be like the passive, afraid Sansa, who in our world would be that shy introvert absorbed in her stories that, when she was young, were her best friends, and who is just trying to get by. And it's refreshing to have a main character in such a dark, high fantasy series who's like that; a completely average human character (and also magic-less, as her storyline is one of the few that doesn't involve it) who is forced to go through the things she must go through. It's part of why I love the series. It's fascinating to watch. She's completely an underdog who is being forced to grow up in the worst way possible and who is doing her best to survive - and so it's easy to want to see her finally get hers.