Well, part of the question is how deep do you want to go? How much do you want to spoil? If you want to keep things basic and avoid spoilers and such, but still want a full explanation of the plot, well...hmm...let's try it with something simple first:
Fire Emblem 7:
The game starts off with Lyn meeting a wandering Tactician, the two embark on a journey together and come across various companions. Lyn learns she's the sole Granddaughter of a noble who is sick, and thus the only heir, and sets out to meet said Grandfather before an ill fate becomes him. Along the way, she also learns her great uncle is trying to usurp the throne in her Grandfather's time of weakness.
A year after Lyn's adventures, Eliwood, a friend of Lyn, and a noble himself, goes searching for his father, Elbert, who went missing. Aided by his best friend Hector and his most trusted knights and friendly locals, he discovers a plot by an evil wizard named Nergal, who using a rival noble in Darren (was that his name?), and a band of thieves known as the Black Fang, wishes to take over the world. After what seems like a small scale war, and releasing some legendary weapons, Eliwood and his friends successfully fight off and defeat Nergal.
yeah, I left out some notes like, say, anything related to Ninian, but trying to not be too complicated, and trying to get the point across. You can add along the way toss in stuff like "The quest ranges the entire world, encounters with Dragons from a forbidden land" and what not. Granted, maybe it would have been easier if I chose a game with better plot than FE7, since that game isn't exactly well known for it.
