It would start out as a farming simulation, much like Harvest Moon. Eventually, you can amass 8 cows, a horse, 12 chickens, 6 sheep, a cat, and a dog. Your farm encompasses several acres, and your children's children help you harvest crops. After investing your time courting your desired partner in your isolated, peaceful village, raising your children, and watching them raise their own, tragedy strikes in the form of bandits.
A cruel group of bandits have razed your farm, stolen your crops, slaughtered your animals, and killed your partner, who died helping your children escape. Your grandkids have been kidnapped, and the bandits plan to sell them into slavery. Being handy with a sickle suddenly comes in handy, as you have to sneak into the bandit camp and slaughter your way through to your grandkids. It is not until you confront the bandit leader that you find out this horrid event is part of an overall plot for the king to take over peasant land and give it to his nobles. (This is the Stealth Combat part of the game, similar to Assassin's Creed.)
Unfortunately, the bandit leader gets away, and you know that he will be back with an even bigger force to finish the job he started. You must now help fortify the village and prepare it for attack. (RTS resource gathering and fortification, Starcraft) At the same time, you must travel to other places and learn combat, tactics, weapons use, etc from other warriors, mercenary bands, and the like. (ie Morrowind)
On the road, you meet others with similar experiences or goals (Baldur's Gate), who are willing to fight with you in a party. You eventually track down the bandit leader, the corrupt nobles, and usurp the king. You then become King, and must run the Kingdom through the ages. (ie Civilization)
That's all I can think of, so far.