Don't take this too seriously, but just off the top of my head:
- Foreplay, because there's way more to sex than just pelvic movements.
- Makeup. Seriously is there no alternative other than the whore look?
- Cover art. Really bland next to the flare and some would say photoshopping prowess of JAV cover designs.
- Immersion, for the lack of a better word. Western porn tend to be over-acted, while JAV has the knack for depicting real life surroundings easier for the audience to connect to. Lacking even the flimsiest disguise of a plot doesn't help either.
- Variety. JAV basically observes Rule 34. It's hard to measure up to that but doesn't mean you shouldn't try.