IMO Sennheiser produces the most natural/neutral sound, as it probably has in the past as well. Can't really say about the past, but if you look at their current line up:
More or less neutral with perhaps a touch less bass and a touch more treble.
Refined HD 800
One of the least neutral/natural of the Sennheisers but still measures at least as good or close to the best measuring AKG or Beyer phones.
As flat as you'll get.
HD 600 with a touch more bass and a touch less treble. Second in FR only to HD 650.
More or less neutral with forward mids. Still more neutral than most.
When you keep the above in mind with the fact that they better warranty/service, are very comfortable, easily available, similar global pricing, it almost becomes a no brainer.
The only other company worth considering is perhaps Mr Speakers but outside USA they will probably end up very expensive. And of course Sennheiser has a wider and more diverse range and other factors mentioned above.
But unless you're deliberately looking for colored phones, I'd guess Sennheiser and Mr Speakers pretty much the best out there.