He gives Superman the appropriate amount of youth and makes him look like a real hardened leader.
People say he makes Superman look angry too often, but that's just the circumstances of his stories. Besides that, SO WHAT? Nothing looks more bad ass than an angry Jim Lee Superman. Not many people can do it like him. Besides he is able to draw Superman as looking very calm and serene as well; http://www.dialbforblog.com/archives/325/jim_lee.jpg
Normally, I'm not a fan of his artwork in comics--but in All-Star Superman, it worked perfectly. Tbh, I don't think any other type of artwork (with the possible exception of Alex Ross') would have suited that story.
Ed Benes is a great one, probably a close second for me.
He and Jim Lee's are very similar as far as build goes. But Benes Superman looks a little younger and thus less defined in the face. Benes Superman looks friendlier, more heroic at times maybe. And Jim's is more stoic looking, and invokes more of a warrior image.
Gary Frank's Superman was very distinct for the eerie resemblance to Christopher Reeve. Never saw anyone do that before.
I know he's one of Alex Ross top characters to illustrate, but to me his signature character is Captain Marvel. He's got the Best Artist award for him hands down, in my opinion.
Have to give mention to the great work done in years past by George Perez and Shane Davis, too. When Ron Frenz was doing him in the 1990's, you also got a real sense of how Superman would be done at Marvel Comics, with his John Buscema-influenced style.
...But right now, with the spiffed up suit, Jim Lee holds the title.
"I'm not smart so much as I am not dumb." - Harlan Ellison