These cliches stem - not from mythology and legend (which is where the inspiration of Tolkien, Lewis etc draws from) but rather books of these renowned writers. Writers often disguise this blatant plagiarism with one word: inspiration.
There's a line between inspiration and plagiarism. For example, depicting warring cultures in a magical land is inspiration but depicting warring elves, dwarved, orcs and humans in a medieval words with one exceptionally evil wizard with no motive is plagiarism.
So far these cliches have come up in many succesful books,
Harry Potter by Rowling, The Inheritance Cycle by Christopher Paolini, Wizard's First Rule by Terry Goodkind, Twilight by Stephenie Meyer, Some of these cliches are:
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The hero is a teenager-something farboy/shepherd/smith/thief/prince that gets super-grand power.-
The heroes are orphans or with a doddery fool for a Father.-
Someone close to the hero is killed at the beginning thus entirely motivating him to seek revenge.-
There is always a mentor (typically an old lady or a bearded grandpa) which is a hidden magician with super-great powers. [Merlin(original) - derivitives are Gandalf(though Tolkien admitted himself that he was derivitive of Merlin, Brom, Dumbledore, Zeddiculus Zoriander)] -
This mentor sometimes turns out to be using the hero for his own nasty purposes.-
THE GREATER GOOD conflict comes up at once place for another. (there are more philosophies that seem equally controversial and conflictual)-
It's a black and white world - the evil ones are so, terribly evil and the goods ones are so, wonderfully moral. (impossible)-
The hero falls in love with an unuttainable girl which he ultimately attains anyway!-
The plot involves a quest to hunt for something - magical stones, gems, boxes, rings etc. (Boxes of Orden, Horcruxes, Belgariad)-
Dragons, Wolves, Werewolves, Vampires, Sphinxes (kill me, gag me)-
Difficult-to-pronounce names with dashes and apostrophes (Wh'at-tf')
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Bigotry of a race (although I think this I approve of this, bigotry is every world)-
Fortune-telling 
(God this happens a lot)-
The Damsel in Distress 
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Entry from modern world to a medieval and imaginary one. -
A Bard that tags along to sing stupid songs and show off the author's ability to songwrite which is partly like George Bush on karaoke night. -
A midget is present in the group for no purpose other than comical relief. -
The evil overlord villain or the old-mentor somehow turn out ot be related to the hero. -
The hero is related to royalty or someone in the story inherits the throne. -
People go around clean-shave in a medieval world which was not really how it used to be all the time. Shaving, cutting your hair - it was all very expensive. -
The kings and nobles are so caring about people - wrong, medieval world monarchy cared NOTHING about people. -
Hero has an evil twin/brother/sibling. -
Hero somehow defeats a gladiator-inspired bad guy at the start no matter how inept the hero is ( the odds of that are really slim)-
The perfect ending where everyone is happy despite the fact the world is war-torn and there are BOUND to be casualties. These and more are some of the cliches that just HAVE to be avoided. Yes, a measure of cliche and originality can give a great story. People need an air of fimiliarity to get into the story, but the things described above are definitely too-much.
Go and write your story, please.
NOW!
The list is open to your contributions.
Asfand
Adding your comment:
Then out comes a witch from the unusual house, replace the chickens feet with candy canes and bingo! Hansel & Gretel are formed. From Baba Yaga, other fairytales have been derived such as 'Snow White' where Baba Yaga is a conniving step mother. 
) but my latest fad is now Werewolves. Even though I'm writing my own ideas of what Werewolves are like, I acknowledge I 'steal' what I like but I disregard the rest to create my own monster, similar to what Dr. Frankenstein did with body parts. I'm enjoying watching/ reading a whole host of Werewolf movies and books where I promise my anxious friends, "purely for research purposes of course." 
