Dorian and Ronnie (mainly at the beginning of his reign) had far more competitive line ups. Lee was up there with them in physique but no-one ever pushed him until Dorian in 1991.
It got tougher every era. Arnold only competed against a handful of guys during his career but Haney competed against a much larger field but no one could challenge him genetically. He was
much taller and bigger (with a small waist) than everyone else. You're right, Dorian was the first guy who could really challenge him in both height, width and thickness. Dorian probably had the
most competition with the new freaks in the '90's (Flex, Levrone, Ray, Dillett, Nasser) and the drug use also increased big time.