Bah. All you whippersnappers just talk about your befangled new games, or popular old games. How about suggesting something A LITTLE outside the box? Although Sanctus, when you say it HAS to be in the medeival era you are really restricting us from a lot of good stuff. Anyway.
RTS:
King arthur, the roleplaying wargame:
This is basically Fantasy - total war. This is the ONE game I would check out if I were you. It has city management, large battles, micromanaging your kindom with laws, fiefdoms, alliances, tech trees, choose your own adventure-type quests etc. etc. etc.
Battle realms:
Old game, don't know where you'd find it, but surprisingly solid and inovative combat system. Liquid really outdid themselves with it IMO.
Warhammer - Mark of chaos (and Expandsion)
Not the best game in the bunch, probably best for those who are fans of the warhammer genre, but it might still be worth looking up.
Majesty 2:
A remake of the old Majesty game. Much higher pace, quite hectic, but all the love, humor and fun is still left. To paraphrase Yahtzee: If one of the only things i can complain about is that the game is too short, it's probably pretty good.
Kohan 1 - Immortal sovreigns / 2 - kings of war:
Again older games, but much like battle realms worth checking out simply for how they handle staple RTS mechanics like units, resources and such. Very interesting game.
Warrior kings 1
Great old game, with one glaring flaw. It's awesomely horribly slow. But I still loved it since the whole "returning for vengance" storyline works so well when paierd up with leading pagan hordes of barbarians and deamons to kill your former foes. Second game was not so good.
TBS:
Hard one, not many good Medeival styled TBS games have hit the shelves in the last....200 years or so. The only ones I can think of from the top of my head (and the top of my gaming shelf) are:
Kings bounty:
A remake of the old kings bounty games that predated the HoMM franchise. Well worth a look and if you enjoyed the first game there is a improved (but not innovative, just more of the same, but better) expansion.
Age of wonders 1 - The wizards throne / 2 - Shadow magic:
If you ever played and enjoyed the master of magic game. This one is for you. It's possibly one of the better TBS games to have hit the shelves for the last decade or so and def worth a look.
RPG:
Not my forte I'm afraid, but beyond what ahs been said I guess I should add:
The witcher:
Now, now, some people hate it, some people focus completely ont he fact that you get a lot of sex with no effort. But in all seriousness this is what Dragon age should've been striving for when they said "dark fantasy". There is misery, there is alcohol, drugs, dead woman and children, constant mood of foreboding doom etc. The witcher has it's flaws, but personally I prefer it to the appalingly standard gameplay of dragon age. One can hate on the sex, and the sub-par combat system of the witcher, but in terms of mood and difficulty (at least play on hard) combined with using russian + subtitles really makes for a immerisive and fun experience IMO. Something that dragona ge never delivered for me.
Gothic1/2/3:
Never played, but it's been highly reccomended by many friends. Please check it out in your own time since I have nothing to say about it
-------------
I could go on with some of the more "colorful" fantasy titles out there ("Sacrifice" anyone? Or maybe heroes of annihilaited empires?). But this is what I have off the top of my head in terms of medeival fantasy. And also all I can be arsed to write
Happy gaming.