IMHO a gears up landing on a runway in no way requires any special skill
The 767 . like many othe large twins has the engines hanging well below the main fuselage , a couple of inches asymetrical and you could end up like the Ethiopian 767 who did this on the water some years ago,
Of course, as "Sully" himslef says :an amount of luck was required ... but as a glider pilot himself he knew that wings absolutely level is an absolute prerequisite when attempting such a thing. So superiors skills , yes.. in both cases.