King Arthur: the role playing strategy game is decent. Though it gets pretty frustrating sometimes.
This game has great potential and would be one of my favorite games if it was not the absolute worst optimized game ever made. It gets so goddamn laggy and twitchy with barely even half and army let alone a full army.
That aside I would say Crusader Kings 2 is really in depth. Game is nothing but you making choices on all kings of levels. Who to attack, who to marry, what kids to pay attention to, what generals to evolve, the list goes on for days. And even with those points there is a hell of a lot of depth with just them. Tons of character traits that can either benefit you and the next generation of your family or hurt them.
My top rts games of all time (in no particular order) that I can think of off the top of my head would be:
Total war series
Warhammer series
Age of Empires series
Kessen series
Command and Conquer series
Sid Meier's Pirates (rts/rpg hybrid kinda)
Supreme Commander 2
And Starcraft 2 even though it was only a trial version a got to play a couple levels for a few hours and was still fun.