I generally charge a lot to bare with people.

Anyway, Northwest isn't a bad option between Singapore and Tokyo. Main thing to mind is that their equipment varies A LOT when it comes to the experience in economy class. I believe they use A330s on this route, which are very nice in the back. Their 747s are awful, though. Business class is more consistent.

ANA and Singapore Airlines are both much more pleasant in any part of the plane. JAL should be at least as good as Northwest. The other option is United, which is still a few steps below NW in terms of product and service quality.