For The Arthurian Legend, Harry Potter, Star Wars, and the Ring Trilogy.

Basically, A bildungsroman (coming of age novel) written by the elderly for the imagined edification and indoctrination of the young. The aging writer tries to recapture the idealism of youth, with its clarity, innocence, moral certainty, loyalty and determination to succeed through perserverance. Basically, its propaganda for surly selfish kids, written by disillusioned, tired old farts. But the formula works, which is why we see it so often repeated. The wise old coach guides the noble young athlete (with the aid of the spunky team of misfits) to defeat the cheaters. Its all designed to reinforce the virtues the aged always see as lacking in the young: loyalty, perserverance, and self-confidence. Its pretty obvious and quite shameless, really. Its one of the many basic themes in mythology.

Young Hero: Arthur, Harry Potter, Luke Skywalker, Frodo Baggins
Old Mentor: Merlin, Dumbledore, Obi-Wan Kenobi, Gandalf
Nasty Villain: Mordred, Voldemort, Darth Vader, Sauron
Wacky Sidekicks: Round Table, Harry's friends, Luke's Allies, Ring Fellowship
Magic Weapon: Excalibur, Elder Wand, Light Saber, Sting
Warrior Ally: Launcelot, Sirius, Han Solo, Aragorn
Hottie: Guinevere, Hermione, Princess Leia, No sex please, we're British