How is this even a question. Pampered modern divas like Lewis don't belong in the same hypothetical ring as Gene. Glass jawed fraud Lummox gasses by the 3rd after Tunney bamboozles him with Astaire level footwork using his size against him before leaving the big oaf spreadeagled on the canvas spark out. Tunney KO 3
Lewis obliterates Tunney with the first punch he lands. Which might be a while as Tunney would be running away like a frightened rabbit from the first black fighter he ever got in the ring to fight.