One thing that springs to mind is that D&D has a very prominent tactical/strategic aspect to it. By that I mean that characters & players are expected to do quite a bit of planning for the character's progression, for eliminating bad guys, for dealing with the situation at had, for navigating down the corridor to get to the end.
I cannot think of any other RPG that encourages "optimal" behavior or the extent of contingency-planning that D&D does. The extent of paranoia is not unique, but planning for any eventuality, is. The 10 ft. pole and the bag of holding, I'd say are the embodiment of this principle. The pole lets you stay out of harm's reach while still being a tool for getting past the obstacle, while the bag lets you carry all manner of gegaws: caltrops, burning oil, rope, pitons, crampons, breathing straws, pastel plush pigs.
Perhaps it's just an artifact of games of that time period, I don't know. But I'd say with respect to those games, they *all* were D&D, in essence, just with different, and sometimes not-so-different, rule sets.