LIke what cjl said our technology isn't perfect, every manufacture will choose which part of the sound they want to sacrifice that best appeals to their target market, so even high end headphone have sound signature. Its like cars even though lambo, ferrari and GTR all can reach 250+km/h, The comfort, steering will all be different. All of them will be fast but in their different ways. Just like headphones I don't think anyone going from a sennheiser HD555 to ANY of the high end headphones will think that hd555 is over all superior. But each of the high end headphone will have an area where it excels in. In the end its up to the buyer to see which part of the sound is most important to them and what should be sacrificed in order to achieve that.
I personally really like HD800's sound stage and i am willing to sacrifice some bass in order to obtain that superior sound stage. I also have a LCD2 when i need some extra bass. ( just get every thing lol.)