I have pretty severe neck and cervical spine degeneration, and have gone through literally dozens of pillows trying to find something that worked for me.
After many years of searching, I tried a pretty unique "side sleeper" pillow from
Sleep Artisan. It has a boomerang like cut-out (vs being rectangular in shape) so that your neck fits up "into" the pillow. It also has a combination of all-natural latex and microfiber poly silk "chunks" as filling and is openable so that you can remove or add material as needed to find the level of support that works for you. You can also buy more filling. I did buy some thinking I'd probably need to add to what the pillow comes with, but so far it's still in the bag unused as the pillow provided plenty of support for me. Guess if the filling ever does start to break down I can easily replace it, so the extra filling is maybe good to have for that reason..but so far, more than a year in, I haven't noticed any change in firmness from when it was brand new..
In addition to the degeneration issues, I have what DW lovingly calls "a big giant pumpkin head"
. So, I needed something with really good support. I used to use 2-3 pillows to get the support I need as traditional fills wouldn't hold my head up properly. When I got the Sleep Artisan pillow, I still used two at first - a soft down pillow on top of the Sleep Artisan one..but since have found that sleeping JUST on the Sleep Artisan pillow is still plenty to provide support - and it seems to align my head with my neck and spine a lot better.
LOVE this pillow. It's expensive at ~$109 for a Queen, but worth every penny IMHO.