I don't think make up is necessary. The girl I like never wears any make up. I have a friend who wears make up, and she looks nice with it on, but she's also pretty without make up. The thing is, she doesn't over-do it, but some girls do.
Some girls wear so much make up, that you can barely see their faces anymore. That's kinda bleh. It's like they're wearing some sort of mask.