[In this fake series (that maybe will become a real series if I or others feel like it), I turn the Destructoid original series "Games Time Forgot" on its ass and instead discuss time periods that games just don't seem to explore.]
Like this, but not.
Living in the Early Middle Ages--sometimes referred to as the Dark Ages--you've had a hard life so far. You managed to escape Rome before its downfall, narrowly missing the arrival of Germanic tribes and large-scale war with the Goths. You traveled to Britain and somehow arrived unharmed despite the constant threat of barbarians and smallpox. You kept yourself fed despite economic and political collapse and extended periods of agricultural struggle.
Luckily, you're trained in the use of swords, but with threats seeming to come from all around you, how long can you hope to last?
If this sounds like a great setup for a game, I would completely agree with you. However, aside from strategy games that allow you to tinker with the history of this period and dozens of RPGs that use medieval times as a springboard for creating new fantastical worlds, the Dark Ages--and the Middle Ages in general--don't really get a lot of treatment. Could a true medieval (no, not Medievil) game really work? Read on.
The Life and Times
Throughout the Middle Ages, a lot of shit happened. Religions struggled against each other, bands of fighters clashed, castles were constructed and torn down in terrible ways, and city life became nothing but a memory. Until relatively recent years, not much was really known about the Early Middle Ages, and now that we know more, it perhaps wasn't as dark of a time as many believed. Though there was plenty of war and suffering, there was a fair share of artistic and intellectual development.
Still, it wasn't fun. Those who weren't living life in the filth were the few warrior nobles in existence--those who lived and died by the sword. Before chivalry emerged, there was simply killing for money and survival as warriors on horseback traveled to collect taxes for those who had laid claim to land. Lords competed with each other for the loyalty of the peasants, who in return had very little to offer. The clergy attempted to gain a foothold, though it lacked organization and true power.
Does this not sound like an incredibly rich setting for some meaningful storytelling?
Creating a compelling game in this setting could seriously work. With any of the struggles mentioned above, a mature and realistic story could be told. A lowly peasant could learn the ways of the sword in order to fight for a better status for his family, rising through the ranks and coming under a lord's power before realizing that this life isn't any better. A trained knight could fight in patchwork armies against the many Germanic invaders. Or a more open-world experience could be provided where any number of these elements could be combined to give a comprehensive experience set in this time.
As for genres, many of them could work, from a first-person experience akin to Oblivion to an all-out action game like a toned-down God of War. We could have a traditional RPG or (yet another) strategy game with a more narrow focus. With the right story, any of these could provide a rich and original experience.
Why We Probably Won't See It
Thanks to stories of King Arthur and his favorite magician, Merlin, it's probably unlikely that we'll see any sort of realistic games set in the Middle Ages. Medieval times on our own world have largely been forgotten, instead replaced by created worlds where magic can lend a sense of wonder to an otherwise unsophisticated and dreary existence. For this reason, making a game without these elements might be considered too risky by developers or publishers.
We still have games that are somewhat similar, at least. Bioware's Dragon Age promises a low-fantasy tale with plenty of maturity, and we'll always have the occasional RPG or strategy game that lets us visit castles and swing swords.
But I know that a great game is just waiting to be made here. Despite a lack of realism, I think games like Assassin's Creed proved that games set in historical periods can indeed work in the hands of a skilled team. And, come on, who doesn't like knights?