It's not that I don't like the Koopalings, it's just that I like Bowser Jr more. He's an oddball for his status, really; he's the spitting image of his father, yet clearly isn't a kid version of his father given that he acts rather differently to Baby Bowser. Odd, really.
I've always preferred to the Koopalings. It's not that I hate Bowser Jr., I just don't really think much of him. I did, however, like his Shadow Mario disguise, though. That's mainly because I happen to like characters who are evil halves/clones of others.