Given the options, I think that a decent argument can be made that emacs is the best editor, and that it's unreasonable to use anything that the best — so yeah, one might argue that emacs is the only reasonable editor.
I don't know if I'd go quite that far, but I wouldn't instinctively disagree.
My take is Emacs is the best integrated text processing environment available. But I am not sure it would beat VI/VIM as an text editor.
I don't think most Emacs users could match a good VIM user in text editing speed, but then Emacs can do many other tasks that are hard to replicate in VIM, while being a more than good enough editor.
It is not so much which editor is better, rather what are the user's expectations.
To me this is obvious and has been probably been said a 1000 times before, but sometimes when reading threads about text editors, you would not think so.
Given the options, I think that a decent argument can be made that emacs is the best editor, and that it's unreasonable to use anything that the best — so yeah, one might argue that emacs is the only reasonable editor.
I don't know if I'd go quite that far, but I wouldn't instinctively disagree.