J.R.R. Tolkien invented his own original series of novels in the 1930s, with ideas taken from Sir Gawain and the Green Night and other old tales from the days of old, but only as inspiration. He invented his own language, his own world, his own characters, and his own monsters. I cannot see why this can't happen again. The human mind is an amazing entity, I guess people aren't being payed enough to think of anything original. Or people are too worried about themselves because they're suffering in these hard economic times.
Bethesda invented their own world (Nirn, Tamriel etc.), their own language (Dragon Language among many others), their own characters (Every character in the entire game), their own monsters (Spriggans, Wisps and Wispmothers, Atronaches, Hagravens, etc.). Shut up and get out.