Healthy people come in all shapes and sizes... For example, not every person who is super skinny has an eating disorder. And not every big person eats like crap and doesn't exercise. It's the lifestyle, not the number on the scale.
As for what is personally attractive to me, I like curvy/thick (probably what most people would call fat) girls and lean guys. Just my personal preference. I don't have an opinion as to where others "should" be in terms of size, because we're all different and who gives a f***. It's their body, not mine.