You're right, darkelf. You shouldn't change who you are to fit a guy's needs. If a guy wants a girl who's more like Paris Hilton, then he should look for that in someone else and not force you to conform to what he wants.
It still hurts though, believe me. But if a guy can't or won't accept you for who you are, even if you like him, he's not worth it.
There are some sincere ones out there. Just gotta keep your eyes, heart, and mind open.