I don't think that the quality of Kojima's work makes it critical to games going in this direction, because they were already going that way.
There was already good work being done that would have continued with or without Kojima.
The quality of Kojima's work is precisely the reason games were able to evolve so quickly into what they are today.
Because MGS did it so effortlessly, it raised the bar while providing a blueprint for how a cinematic interactive experience can capture the imagination and hearts of it's players even if you have a shadow for a face.
Sure it would have happened eventually, But how long would we have had to wait?
Take 3D games for instance... They were inevitable and they had many people failing at creating something fun or even playable. There were some successes, but everyone still preferred moving a character in 2D than 3D.
Then Miyamoto not only shows them how to properly move and JUMP with Mario in 3D...
...He also gives Link a targeting system so he can properly attack the enemies in front of him.
Now, because of his contributions, other developers know the answer to the problem, they now have a base to start from and find ways to build off of what they were struggling with for so long.
You can say the systems or techniques made in the past would have come up eventually because you are enjoying the evolution of those systems. Some of us older gamers know the struggle was real for developers trying to handle not only how to tell a story, but just how to move the character.
Saying it's inevitable is a no brainer because everyone in gaming was trying to figure it out. What's amazing is that not only did someone figure it out (out of hundreds of developers), they figured it out so well that you don't see how it could have been done any other way. Yet at the time,
no one came close to providing the same feeling or level of polish as the pioneers did until AFTER they showed everyone how it's done.
As inevitable as something may seem it still takes hard work to realize, and not to take anything
away from PDS, but MGS was on another level as a whole. When people bring up the cinematic nature of MGS. They aren't talking
about JUST the cutscenes. As amazing presented as they were for the time players remember the entire game giving them that cinematic feeling of being IN a spy movie. Not simply playing a game.
As inevitable as something may seem, it still takes hard work to realize. Not trying to take anything away from PDS, but MGS was an entirely different beast that did so many things right in an era were games were trying to figure out the newly created 3rd dimension.
When people bring up the cinematic nature of MGS, they aren't talking about JUST the cutscenes. It's the pacing, the gameplay scenarios, the radio drama, all it's parts that was the result of a lot of people's hard work, but also a single man's clear vision of a different type of game that made you feel like you are in a high stakes spy movie, and not just playing a video game.