Most people look better after jaw surgery, IMO, because the jawline is really important for overall facial attractiveness and a lot of us have something significantly off about our faces. I don't think there are many people who are "really good looking" before jaw surgery as it is quite rare to have significant functional problems without it showing in the facial structure.
I've had various 'PS' procedures, minor and more major. Chin lipo? Looked great. Botox to raise the edge of the brow? No-one asked me if I'd had botox, I could still move my face, it was subtle and looked natural (I didnt get other areas, though) My rhino didn't change the size, just the shape of my nose, and I don't think it looks fake. My other Father didn't even notice! Sure, some nosejobs look bad (I've seen a lot of bad ones here in the Middle East) but subtle rhinos often look great. Scarlett Johannsen? Blake Lively?
PS usually looks bad when people go over-the-top (e.g. getting 3 syringes of Juvederm in their lips instead of 1, or getting a teeny tiny pointy nose, or big fake boobs on a small frame). Some of the older eye jobs and facelifts do look pretty bad though - modern techniques are definitely better