I'm an admitted Amsoil fanboy and dealer so I will be using them.
For an on the shelf, paper element oil filter I generally recommend Wix if Amsoil doesnt have a filter. Wix is the OEM for a bunch of manufacturers.
For a long time Amsoil(Baldwin/Hastings is their manufacturer) was one of the only suppliers that offered a synthetic element filter, not paper element. I believe this has changed and a few other companies are offering synthetic elements now also.
I will add that i have used Mobil 1 filters, AC Delco(I believe made by either Wix or Fram), K&N, Harley(probably also Wix or Fram), Mann and probably at least a handful of others. Never REALLY had any issues with any of them. If you want some in depth analysis head over to BITOG and see if somebody has taken apart one you are interested in. Most of the big makers have been disassembled and compared.