From what little I know, Bose has patents on a number of noise-cancelling techniques, hence making it tricky for other manufacturers to match them in noise-cancelling. However, in the past five years, several other manufacturers have done pretty well (though I believe some cross-licence patents with Bose), and Sony and Apple do lead in some comparative reviews.

It is a shame that Bose's lead in noise-cancelling isn't matched in the quality of their sound.