A lot of it (just like with WIAB) is that it perfectly fits the scene. So it's not just the music itself, but it how lends itself and increases the emotion of a scene. Something imo, Ocean is quite unparalleled at.
...
I remember Oceans saying that he actually builds scenes around the music that he happens to find and like, not the other way around. This is why the music fits these cinematic scenes so precisely. And it's obviously quite impossible to simply replace the soundtrack of such a scene and get the same results - the feeling, visual, audible and emotional impact.
What I also like a lot is that Oceans games make you feel as if you were watching a movie, although most images are static. They just feel like movie scenes, because they are made as if they were: the locations are treated as movie sets with the camera placement, zoom level, depth of field and scene lighting and the placement of the characters. Maybe not always, but often enough to notice.
I haven't seen another VN that has this kind of feeling. PhillyGames has been trying to do the same and is pretty good at it, but I still like Oceans work better. This could be a personal subjective preference, because I am unable to explain why exactly.
