Naaah, PNGs > JPEGs. PNGs compress like folding your clothes nicely in the drawer. JPEGs compress like shoving 10 pairs of pants into a sandwich bag. Granted, you can get really good results as you said if you set it up correctly, but the automatic settings usually make everything super pixelated.
Are you using a DSLR? You can eradicate a lot of that noise by using natural light to your advantage!
I agree about PNGs though. I remember when I used to do pixel art in MS Paint and I hated JPGs as it had HORRENDOUS compression. Photoshop can handle it okay though. But I'm certainly not recommending anyone save their pixel art as JPGs.
You're not the first person to say that, I really need to stop assuming everyone is into photography...
It stands for Digital Singe Lens Reflex - It's what we call photographers cameras. The big ones with huge lenses etc. Ah well, at least I've managed to educate you this time. (Not the other way around!)
JPEG is much better than PNG for photographs. The reason your picture quality is so poor, is that the sensor is tiny and low quality - that results in a lot of noise (graininess), and then to try and compensate for that the camera will have some very aggressive in-camera noise reduction, which means you lose all the fine detail; as well as image sharpening, which causes that halo effect in areas of high contrast (most obvious around your arm in the 3rd pic).
Unfortunately, that's what you get with webcams, mobile phone cameras, etc - there's just no substitute for a big sensor and big lens.