I dunno, some of the games I've seen on Nutaku are very obvious about the sex - Girls Kingdom and Phantasma come to mind. And I think at least some of the games that are more tame about it (outside the sex scenes themselves) actually have non-X-rated versions, so they're much less vulgar simply by virtue of not necessarily being H-games.

I think it really depends on which Western games you're comparing to which Eastern games, and there are definitely some vulger Eastern games out there...