There are:
Guys who have great genetics and train hard - Dorian Yates, Ronnie Coleman etc
Guys who have great genetics but don't train hard - Paul Dillett etc
Guys who have poor genetics and train hard - can be seen in all gyms
Guys who have poor genetics and don't train (hard, if at all) - they are everywhere.
And all kinds of variations, combinations and cases in-between, running the whole gamut. It all boils down to the individual and their attitude.