Which polls are you looking at? Because pretty much every single one I've seen outside this forum has Kelly, Tulisa and Gary interchanged depending on the website with quite close margins between all three of them. I don't mean to be rude but I wish people would stop projecting their own opinions as "public opinion" and actually give us some evidence for their claims.
As for Kelly being obnoxious and aggressive, I guess it's all relative. To me she's strong and assertive with her opinions, which is refreshing to see in a female judge. Often they're forced to take on a more submissive role while the male judges compete to see who can be the alpha judge (see US X Factor). I don't think she's ever really crossed a line for me and honestly I haven't seen a hint of "arrogance" that most people claim she has. On the contrary, I think she's someone who understands how hard it is to make it in the music industry, who's been humbled by her own experiences and is just trying to get the contestants back on track.
As far as why I like her as a judge, I just really appreciate her comments. She seems to be someone who actually KNOWS what she's talking about. I do like Tulisa but I don't think many of her comments hold a lot of substance. Kelly talks about the tone, the tuning etc. & I think is one of the few judges this show has ever had who really focuses on the voice. I find myself agreeing with a lot of what she says, or at the very least appreciating her feedback. That's ultimately what I look for in a judge, hence why Kelly is my favourite.
But different strokes for different folks.