Wow, this is tricky because all of my favorites are from a long time ago, so they seem a bit dated. I loved FIRE SONG by Catherine Coulter (but in a re-read, the hero is brutal to the heroine) and EARTH SONG (which stood up surprisingly well) by the same gal.

Still love A KINGDOM OF DREAMS by Judith McNaught. Love any of Julie Garwood's Scottish/Medievals, but they are lite on the accuracy.

One of my all-time favorite pleasure re-reads is Jude Deveraux's THE TAMING (about a heiress that marries a very filthy knight) but it's just light all around.

Are you looking for fluffity-but-fun or actual nitty-gritty medieval? I've heard good things about Roberta Gellis's Roselynde series but I confess I've never read them.