All speakers being compromised it's hard for me to single out "best."
But in terms of realism, the most realistic sounds I've ever heard from a speaker came from the MBL 101s (one time at a reviewer's house, another at a dealer). It made all other speakers I've heard sound like they were just "trying" and like collections of boxes and tweeters.
That's not to say the MBLs are perfect of course, just that when playing the right material I haven't heard anything that real.