The Collaborative International Dictionary of English v.0.48:

Unparalleled \Un*par"al*leled\, a.
   Having no parallel, or equal; unequaled; unmatched.
   [1913 Webster]

         The unparalleled perseverance of the armies of the
         United States, under every suffering and
         discouragement, was little short of a miracle.
                                                  --Washington.
   [1913 Webster]

WordNet (r) 3.0 (2006):

unparalleled
    adj 1: radically distinctive and without equal; "he is alone in
           the field of microbiology"; "this theory is altogether
           alone in its penetration of the problem"; "Bach was
           unique in his handling of counterpoint"; "craftsmen whose
           skill is unequaled"; "unparalleled athletic ability"; "a
           breakdown of law unparalleled in our history" [syn:
           alone(p), unique, unequaled, unequalled,
           unparalleled]

Moby Thesaurus II by Grady Ward, 1.0:

74 Moby Thesaurus words for "unparalleled":
   best, beyond compare, beyond comparison, champion, choice,
   consummate, easily first, elect, elite, exceptional, extraordinary,
   fabulous, facile princeps, for the best, greatest, handpicked,
   immortal, incomparable, indescribable, ineffable, inimitable,
   invincible, legendary, marvelous, matchless, mythical, noteworthy,
   nulli secundus, only, optimal, optimum, paramount, peerless,
   phenomenal, picked, portentous, prime, prize, prodigious,
   quintessential, rare, remarkable, second to none, select, singular,
   special, stupefying, stupendous, sui generis, superior,
   superlative, supreme, surpassing, unapproachable, unapproached,
   unbeatable, unequaled, unexampled, unexcelled, unique, unmatchable,
   unmatched, unparagoned, unpeered, unprecedented, unrivaled,
   unspeakable, unsurpassable, unsurpassed, unusual, very best,
   without equal, without parallel, wonderful