I've had stick nuff times for this but i stick to it i really really really think a Prime Tyson would give ANY heavyweight (including Ali) from any era alot of trouble. Thing with people like Marciano aswell was that he would catch Ali sooner or later im sure and he did half pack a punch even though i know he was MUCH smaller and would more then likely be clearly outboxed to a one sided UD but you never know. As has been said its very tricky to compare the fighters frm different eras becuase of size differneces, modern fitness technologys that some fighters get the benifit of and of course diet etc.