Well, you only have somebody's (read media's) opinion on Bird. I don't think he was anything special.
True he had greater opportunity than most umpires because he was an English umpire and as you know, the system is such that only umpires from Australia and England get accolades and applause. I'm willing to bet there are many Indian umpires in that era who didn't have such opportunities as Dickie Bird who might have been just as good. In fact, my father is of the opinion that Sheppard was a better umpire than Bird.
I agree that he was a well-respected and well-loved umpire, but that doesn't make him the best.
The problem is that subcontinent umpires are rarely recognized for good umpiring. Everybody wants to pounce on them for bad decisions, but they are rarely applauded or recognized.
I think personally the Srinivas Venkatraghavan is somebody who was grossly underrated by the English and Australian media.
It's a shame that you decided to start a poll without a single Indian umpire. That shows the power of the media brainwashing system...
Why not Venkataraghavan when you had included (of all people) Bucknor and Dickie Bird?