This might seem counterintuitive, but trust me.
A Good Day to Die Hard is the first script that was written just to be a Die Hard movie. Ever. The first Die Hard was originally written as a sequel to Commando (or a sequel to The Detective, depending on which source you consult), but when Arnold dropped out, they changed it at the last minute into a Die Hard. Die Hard 2: Die Harder was originally a book called 58 Minutes about a cop named Frank Malone who probably never even Die Harded a little bit. Die Hard With a Vengeance was originally supposed to be Lethal Weapon 4, but that also changed at the last minute, probably because turning Danny Glover's "too old for this s**t" good cop into a "too racist for this s**t" lunatic upset the buddy cop dynamic established in the first three. Finally, Live Free or Die Hard was originally called WW3.com, and it was based on a Wired article. About hacking. No one has ever started a movie with the intention of writing a Die Hard. Good Die Hard scripts are like McClane himself; they're the right script in the wrong place at the wrong time.
It's also important to point out that the better Die Hards started out as sequels to other franchises, and the shittier Die Hards didn't. If you told me Die Hard 5 was based on a magazine article, I'd be worried, but if you told me the script was originally supposed to be the sequel to White Men Can't Jump, I would be so on board.