Re: Fighters from prior to 1990 in todays MMA, who would do best?
There was a big and tough Sumo-wrestler called Raiden in the beginning of the nineteenth century. He was known to rough up his opposition very much. This may be the reason why he never became grand champion, but remained in the second rank ozeki for seventeen years.
Men like Dempsey and especially Jeffries come to mind, as johnstown already mentioned above.
I think of some Okinawan karate-masters, too (Choki Motobu and others).