An Adventurer isn't a superhero, its Indiana Jones. I really enjoyed the Indiana Jones movies, but thats not a type of film that fits with the FF.
Actually it does. The FF were never meant to be regarded as superheroes. They've always been adventurers and explorers of the unknown--that's what sets them apart in the superheroic community. The FF aren't about fighting extra-dimensional bad guys, they've always been more interested in understanding the extra-dimension the bad guys come from.