WordNet (r) 3.0 (2006):

unoriginality
    n 1: uncreativeness due to a lack of originality
    2: the quality of being unoriginal [ant: originality]

Moby Thesaurus II by Grady Ward, 1.0:

33 Moby Thesaurus words for "unoriginality":
   aridity, aridness, banality, banalness, barrenness, cliche,
   commonness, commonplaceness, corniness, dearth of ideas, dryness,
   dullness, familiarness, fustiness, hackneyedness, infecundity,
   infertility, mustiness, platitudinousness, prosaicism, prosaicness,
   prosaism, prosiness, squareness, staidness, staleness, stolidity,
   stuffiness, triteness, uncreativeness, unfancifulness,
   unimaginativeness, unpoeticalness