Maybe the common denominator is a mix of nostalgia for those old boxes and the love of games/gaming in general. While we differ in detail we still may relate to each other in general. (For instance I don't like the american superhero comic style, but the enthusiasm in collecting comic books - yes, that's something I understand.)

A few years ago at university I talked to a stundent of applied social studies and we chatted about hobbies. The conversation went from boardgames, RPGs, wargaming, reenactment to SF-/Fantasy-novels, comics, favourite bands, TV-series and movies and so on. He surprised me when he said "You know what? You roleplaying guys are in fact a quite homogenous group."
Never considered that, because we nerds are able to debate endlessly about why Star Trek is superior to Star Wars or such and never realize we're quite alike...