After serving as a guest judge on "American Idol," our Mark McGrath is thankful he never had to sing in front of Judge Dread -- but some of Mark's music contemporaries haven't been so lucky, as we get Simon Cowell's verdict on today's biggest pop stars.

Let's start with teen queen Hilary Duff, who rose to fame playing Lizzie McGuire. "I like her," Simon admitted. "I can see her appeal. She's the girl next door, isn't she? Every young girl wants to be her."

Next up, Lindsay Lohan: "Same thing," Cowell stated. "It's exactly the same thing."

But Beyoncé Knowles is another story. It's been reported that Simon is not a fan of her voice and her sexy image is lost on him.

But it seems that two blonde superstars have caught Simon's eye. "I was a fan of Britney's early records," Cowell said of Spears. "When I see her doing the whole Madonna thing, it's rather like watching if I had a little sister, her put on makeup for the first time. You sort of go 'don't!'"

Simon's other pop star favorite is Jessica Simpson. "I have a certain respect for Jessica, because Jessica is like an ambitious wolf," Simon said. "She is so on it, in terms of her career, and I think you need that."

So there you have it, TV's toughest judge and his verdict on America's proven idols.