It depends. If my hair & makeup is done, I look normal in pictures. But that wasn't always the case, I used to be really un-photogenic until I perfected my photo smile and learned my best angles. And I always look best when I can use my iPhone to take a photo, because I can see myself using the front camera and adjust the angle etc. I think it's also about confidence, if you think the photo is going to turn out bad because you see yourself as un-photogenic, that nervousness will come across in the photo and make you look like you have a weird expression.
I also find that if you use a camera with a larger lens, you get less of a fish-eye effect on your face and you will look more like what you see in the mirror. (i.e. more normal)