I'm new.

[Chutzpar]

You made Ken look sort of like Iggy Pop.

Just sayin.

It's mostly due to two things- you've made his face really narrow, and you've overdone it on the detailing. Too much detailing tends to make someone look craggy or old.
I've always thought Ken was kinda meant to have a bit of a boyish look to him. He's often drawn with big eyes in comparison to other male characters. If you want to make someone look young or a bit childish, then as well as making the eyes a little big, you want to keep the face detail to a minimum- maybe some wrinkling around the mouth (because Ken smirks all of the time), but otherwise try to keep it smooth.

Also because he's pretty stocky and traditionally masculine you'll want to square out his jaw a bit, too.

Also where are his eyebrows? Next you'll be spriting Ryu without the headband... :c