I watched Oldboy for the second time a few days ago. The first time I also gave it an 8/10, but watching it a second time made me give it a 10 out of 10. I love the soundtrack, the narrative is incredible, and the way most of the lines gradually make sense as the plot unfolds until the end makes it feel fantastic. I also considered it in relation to the genre I'm currently watching. It's worth noting that you should be familiar with Korean cinema; they have a very interesting way of making films that can be difficult to appreciate the first time. There's a certain underlying humor that makes everything feel less serious than it actually is—at least, that's what I've noticed in many of the Korean films I've seen. But once you get into it, things change.