Plebs can't appreciate Ami as the best character in the show by a long shot.
Her interactions with the other characters were the most interesting. Yes, she was a bitch, but that facade covered the fact that she was lonely and frustrated with people in general. Watching her overcome her personal insecurities and actually befriend her classmates was more satisfying than anything else in the show, save the first part of the Christmas episode before Taiga cucked herself. Her comments about how Ryuuji and Taiga were being dishonest with themselves about their feelings about each other were spot-on, and she had fantastic general commentary about people. She didn't abide the bullshit and always had something interesting to say. Yes, she was fairly bitchy, but she was honest. Taiga and Minori spent the majority of the show lying to themselves or others about feelings, and created so much drama through plot-induced stupidity. Those two were unoriginal cookie-cutter characters that we've seen plenty of times before, while Ami was written well, as evidenced by how people like to argue about whether or not she was best/worst character.
Ami may not be likable, but she's the most interesting character from the show.