To me, Die Hard 1 and 3 are just utter brilliant, the original for being, well, the original, Die Hard 2 felt too close to the first film, just a few things changed. Die Hard 3 though, actually evolved the character, we got to see him actually in New York (after all he's suppose to be a New York Cop!) but now years later, divorced, reduced to near enough nothing who's again threw into a situation.
Die Hard 4 may as well not exist, it just destroyed the character of John by making him just a generic PG-13 action hero who apparently struggles with nothing, no longer smokes, drinks, only lightly swears and is now the type of person who's at the gym a lot, I mean, what happened to that regular guy who's life is turning to shit?
It appears only John McTiernan knows how to take the films and turn them into brilliant action films with feeling. So yeah, in summary, Die Hard 1 is just the original and awesome, Die Hard 2 just felt like too much of a re-hash of Die Hard 1, Die Hard 3 is where the characters and concept evolved and Die Hard 4 might as well have a different actor in the role!