I read them all in my teens, and still return to my favourites now. There is something to be said for an author who appeals so widely across the age spectrum, and to so many people.
Some are better and deeper than others. My favourites are - The Unknown Ajax, Regency Buck, a prequel to The Infamous Army. (The latter contains a peerless account of the battle of Waterloo). Spanish Bride, Venetia, A Civil Contract, Bath Tangle, Fridays Child. These are in no particular order, except that I think The Unknown Ajax is in the right place, to be followed by The Infamous Army. I also think that the Unknown Ajax would translate to the small screen very well.
Georgette Heyer has a wonderful way with dialogue and character, and was no mean historian. However I could never get on with her crime novels. Perhaps I should try again.