I think they'd all beat Lee pretty resoundingly and early.
While Lee was obviously talented and crosstrained in both striking and grappling, after reading the Tao I find that everything he knew, while being innovative in its time, is pretty much the norm nowadays. The basic concepts of MMA from timing and movement to stance and guard are all presented in the Tao, but they're also presented in the very first day of an "MMA" class.
He was definitely a forward thinker with the concept of Mixed Martial Arts, but definitely not history's most skilled practitioner.
Sig courtesy of that photo-matic magician limba
I went out the way that I fight. I went out on my shield. That’s it. Done. --Chuck Liddell
My goal is to end my opponent --Carlos Condit