As someone else said, it's important to qualify what you mean by "good genetics." It can mean a lot of things:
1--Structure/shape
2--Responsiveness to sauce
3--' ' to training
4--ability to get not only super-lean, but sickly dry
Dorian's structure was weird. He's one of my favorites, but his arms were odd-looking. I think people are actually wrong to rag him on
development as such; his triceps pose was probably the best in bodybuilding when you consider his crazy conditioning, and his biceps were actually HUGE before he tore one of them. Check the pictures of him taken a few weeks out from the '93 Olympia before telling me his biceps lacked for mass
However, they were attached such that, when huge, they almost would hang off the side of his arms...the real mass isn't as apparent vs. someone like Vince Taylor, who also has long biceps but has outstanding insertion points.
Obviously, Dorian responded well to juice and to training. I still say that if he hadn't torn his left biceps, Ronnie Coleman wouldn't be a multi-Olympia winner. Ronnie's huge and more complete than Dorian (overlooking the calf, forearm, and possible trap "shortcomings" next to Yates), but at the same weights, the two look totally different. At 257, Yates is hard as nails and totally dry. To approach that kind of conditioning Ronnie has to weigh ~245, as he did at the '01 Arnold. Even
then he isn't near as bone-dry. So, yes, Dorian outmasses him. That's especially evident when you realize Dorian is almost as hard at 270 (pre-Olympia pics in '93 again); he doesn't improve his conditioning significantly when he goes much below that weight.
So I think, definitely, Yates had well above-average genetics. Someone with average genetics wouldn't weigh 257 at 5'10" without a 50" waist to match. They wouldn't be able to move the iron Yates does even if they magically doubled their strength for that purpose.
I wouldn't go so far as to say he has the best genetics ever or anything like that, though, since his shape was borderline poor and he
was skinny before he started training. I'd have to give him about an eight-five out of ten overall.
I also think Yates deserved all of his wins. Several guys bested him in a couple of poses (Nasser and Levrone in front biceps for instance), but he soundly whipped everyone in the majority of the compulsories IMO. Fancy dancing doesn't whip superiority in the prejudging.