They're all worth reading to someone.
Hard to say without knowing more about what a person likes/dislikes.
Some of my favorites are..
Sharon Lee & Steve Miller (Liaden)
Elizabeth Moon (Serano/Suiza, Paksenarrion)
Wen Spencer (Tinker series)
Lois McMaster Bujold (Vorkosigan)
David Drake (Leary)
Eric Flint (Ring of Fire)
David Weber & John Ringo (Empire of Man)
etc., etc.