Part of being an audiophile is the pursuit of high-fidelity. That word high-fidelity means "to be as close as the original as possble". Bose has never claim to be high-fidelity, and that is the problem many people have. Yes we all like a touch extra bass, mids, treble depending on the music, but Bose has practcally outright said that an accurate frequency response (the shape of the graph, not the numbers) isn't important. That's why they never publish frequency response specs on their speakers or other audio components.
Bose will design their equipment to be pleasing psychoacoustically, and that means that they tailor the frequency response to be pleasing, but by definition it's not accurate. Most people that are into this hobby are looking to hear the music the way the producer intended you to hear it. That's why frequency response graphs is a nice too, because it gives clues as to how the headphones sound. The shape of the graphs gives you an idea of which frequencies it emphasizes. No headphone is perfect, and many headphones have anamolies in their frequency response, but for the most part, they tend to deviate from a target ideal curve less than Bose products.
You can see that Bose QC2 is clearly slanted toward a bass heavy presentation compared to a Sennheiser HD595
I don't have anything against Bose products, in fact I always give them the benefit of the doubt and hear them for myself before passing judgement. Unfortunately I find them disappointing because they color the sound too much. It may work well if you want to go "wow, listen to that bass", but I believe that the sound is skewed to sound impressive to people that don't have a lot of experience with live instruments or real performances.
