With regards to Horner in general, and Avatar in particular. Yeah, i'm one of the many who's accused Horner of recycling the same two scores over and over in the past, but i flat out love so much of his work (Willow, Braveheart, Aliens, Krull, Kahn, Mask of Zorro, The New World... and on) that it's extremely hard to slight the guy. Avatar is no exception, i thought it was incredible myself, though my personal pick for best of '09 was Zimmer's score for Sherlock Holmes, but yeah, Avatar was awesome.
ASIDE: If by "four note motif" you mean that sinister brass riff, i love it, and when i heard it in Avatar i nearly jumped out of my seat. Probably because it features so prominently in Willow.
As the ancient Tibetan philosophy states:"Don't start none... won't be none...".