Die Hard worked because the character was an ordinary guy in extraordinary circumstances. He was barefoot, outnumbered, under gunned, and got his butt kicked most of the time. When he was in over his head, members of the audience actually wondered whether he'd make it.
As the sequels continued, the character became a superhero. The situations had to become more intense because the character became extraordinary.
I think most of us would agree that many movies are fun when they're tense and you're worried about the characters.
Superman was good. Superman II was also fun because he was outmanned and outgunned.
Star Wars was good. The Empire Strikes Back was good because the heroes were outmanned and outgunned. In fact, this was sort of the point of the entire first reel of that movie.
Star Trek II: The Wrath of Kahn was good because the heroes were outnumbered and outgunned. (See the pattern here?) One of the heroes died. Good film.
Bruce Willis might have gone through some test fittings of capes for this next film. :lol
Andy