Alien is a perfect example of my point. Alien isn't awe inspiring because it is straight sci-fi, it is because it sets a horror story in a science fiction setting while playing with the audience's expectations of what makes a hero.
It's still a sci-fi horror film. It was better than any combination of those genre elements before it (IMO) but it was still a sci-fi movie and Ridley nor anybody would disagree with that. And it's still a masterpiece.
To call Lawrence of Arabia a War film is completely off base imo. It is clearly a character piece; the exploration of a man's soul.
It's about a man's soul in part and his amazing character, but it is also an anti-war film about how the politics and violence of it corrupt the beauty of the land and soul as per mentioned before. But perhaps a better description of it would be a biopic? It's far above most biopics, but it is based on a real man's life but completely subverts and ignores the conventions of the genre.
Goodfellas, the Godfather, Gone with the Wind and even Ben-Hur changed genres. If they were simply examples of the genre in which they found their roots, they wouldn't change them. What a gangster film was before the Godfather, is not what one was after its release. Same with Goodfellas. They provided the genres with a completely need energy, a breath of fresh air if you will.
You seem to be arguing that just because they were better than any other film ever made on the subject matter--on which I agree--that they are not gangster films. No, they are still gangster films. Scorsese has often called himself a "genre filmmaker" because of his numerous crime movies. You can transcend or deeply impact the genre, but that does not mean you're not of the genre. Your argument is that if it is much better than its contemporary films within the genre it has transcended it. I think it has in some ways, but it is still part of it. Example: I think
The Dark Knight was
way better than any superhero movie released before or since. But at the end of the day, it's still a superhero movie despite what its most diehard fans want to say.
Look at what sci-fi has become after Blade Runner. If it was simply what sci-fi was perceived before its release, it wouldn't have shaped the genre the way it has. The Empire Strikes back is a fantasy in a science fiction setting.
Not that a great film needs to change the industry. But if a film does that, then it is a good sign that it is a great film.
So, your original argument is that a "masterpiece" cannot be a genre film. But when there are genre films you consider "great" or "masterpieces," such as Blade Runner, they don't really count because they changed the way the industry and public viewed the genre? I'm getting confused in the muddling.
Anyway, back to your original point, if you are now saying impact on the industry and genre are what measures a masterpiece, then wouldn't Gladiator still count? Nobody had made a real sword and sandals epic that was successful in 40 years prior to it and after Gladiator the genre returned with much fanfare and everyone was trying to copy Gladiator. Many still are. It changed the way people made movies on that subject and similar films. Just saying.