My favourite pokégirl is Iris... Yes, Iris.
I can feel you looking at me with frowning, but I'll try to explain my unusual 'taste' (as Cilan would say).
First of all, I think the reason why most of all hate her is because the anime's producers made her so much different from the game (what is bad, but not that bad). I mean, on the first game she first appear as a promising gym leader (or at least gym leader learner, if you played the Black version) and on the next game, she is simply the champion. On anime, she not even close to this "status" (well, in the last season there is a hint that Drayden wants she to be his substitute, but it don't look to be for a short term). And I think when they (producers) made Iris become weaker over the time, they almost "kill" any charisma she could have (her greatest moment was when she defeat Ash at Club Battle Cup, after this she just loses, and it is (s)bad.
But, there is somethings which makes me like her.
- Her "athletic" style, I mean, she is always jumping, swinging through the vines, climbing trees, and I think it is cool.
- She is a Pokémon trainer... I don't really like the "Pokémon Contests", I'm sorry, I know that many of you must like it, but I not, so when I figured out that Iris, unlike May or Dawn, would not take part in Pokémon Contests, it instantly makes me like her a little more (I want to make clear that I am not saying I dislike May or Dawn, I just don't like what them do).
- I like how she is able to "feel the feelings" of the Dragon type Pokémon, like she did with Dragonite and Axew.
"But she is such a little and boring kid!"
Her "catchphrase" never really bothered me. And, I suppose she still calling Ash a little kid in order to bother him (because on the begining of the series, he indeed made childish mistakes), but I suppose this make many fans angry as well.
but I will say it anyway: I voted for May 
I don't like Ash that much but, the has much more experience than her!!
)
