Law is pretty popular in Japan actually, which is not at all surprising. You may change your opinion about Law if you ever play SMT2, cause that's the game that kind of branded them as the ultimate dicks of the MegaTen franchise. Not that SMTIV did them any favors...

I think Devil Survivor (before Overclock screwed it up) is the only entry I've played where Law is one of the better options. Though bringing this back to the topic of moral choice systems, what I like about SMT is the fact that the stories are really about exploring the factions that support the ideals rather than the choices simply being a way to play your characters. I mean when you choose to burn down a village or save it in Fallout, it's not like your choice affects your standing with the Enclave or the Brotherhood of Steel. The moral system is separate from the grander elements of the story, whereas it's the heart of the MegaTen titles. Even then though, I would point out that MegaTen itself can be pretty simplistic about their mechanics as well and looking back on the franchise as a whole, it's obvious that where you fall within the Law/Neutral/Chaos dynamic has a greater impact in SMT1 than it does in SMT4.